Here'* a fun little story.

A few days ago, on my way to San Fran about an hour and a half from home, my Silhouette overheated. It went from normal to "in the red" within 30 seconds. I was on a bridge with no where to pull over and miles to go before the was anything resembling a shoulder. The car went into limp home mode as I tried to get out of traffic.
Once I was off the freeway, Google maps said I was within half a mile from an O'Reallys. I noticed the fans weren't coming on but I figured that didn't explain it getting as hot as it did.
At O'Reallys I picked up a fan relay, a water pump, a thermostat, a couple gallons of coolant and a new serpentine belt. That should cover any of the issues. And it was getting late so I figured it would be over prepared in the side of the freeway than under prepared.
Popped in the new relay, fans came on and I drove around the hills of SF while keeping an eye on the temp. It ran hotter than usual but only by a little. I got on the freeway and started to head home. It'* a couple miles between the last exit in SF and the next exit. And as soon as I got onto the freeway, it jumped back to the red.
After pulling off, I noticed that the top radiator hose was empty. No pressure at all. So, in my head, the thermostat was less likely and the water pump more likely. I had a crappy little tool set with me, one of those $10 sets they sell near the checkout. Made it a little harder than it should have been but I got through it. Once I got the old pump off, I noticed a couple things 1) the Previous Owner had it filled with water and 2) he had also been filling it with some sort of "stop leak" product. I pulled a fist sized ball of stop leak fibers from the pump and it'* housing. Cleaned it up the best i could on the side of the road and started to put the new one on. Hmm. Big bubble on the mating surface of new one. Can't even get it to fit into place, maybe if I had a file, but probably not even then. So I put the old one back on. It'* got to work better without all that "stop leak" crap in it.
I get a few more miles and it'* back in the red. But this time I notice that the top hose IS swollen. I'm guessing that the stop leak has clogged the thermostat. I've changed a hundred thermostat in my day, no big deal, right? Haha. Somebody at GM deserves a punch in the nose. I'd almost rather give this car away rather than change the thermostat again. Thermostat fails, time to get a new car.
Took me a good 10 to 12 hours to change the damn thing. I might have been able to shave an hour or two off that time with better tools, but I doubt it. Last week I converted my 61 TBird to disc brakes and changed the head gaskets. That process took about 12 hours, granted I did that in my back yard.
So that got me home without issue. So ran a little hot, like it would jump between 1/2 and the 3/4 mark but never in the red. Didn't even want to look at it yesterday so I took my non A/C F250 around yesterday. But I had cooled off a bit today (even though it got up to 106 today) so I changed the pump again. Topped off the radiator and took it for a drive. Right back up into the Red. Top hose swollen again, the overflow reservoir was spilling out. I'm about as hot as my engine. I made sure I spent extra on a thermostat that would fail open. I'm glad I didn't have a hammer with me at that moment. But I just drove it home, in the red. Because, screw this thing, and I was only a few blocks away.
No smoke, no oil in my coolant, no coolant in my oil, no service engine soon light. Just more overheating. Hoping that there'* just an air bubble in the line so I spent another hour trying to get as much coolant into the system. Drove it around a bit more, and it'* still running hot, just over the middle line. But it hasn't gotten back up into the red, yet.
Also, the fan relay failed again.

What am I missing.

Most 3.4 v6'* will suffer a lower intake manifold gasket failure some time in their lives. If left unchecked, leads to coolant contaminating the oil. The contamination leads to mechanical failure, the loss of coolant leads to cracked/warped heads.

I would start checking things accordingly and flush the coolant system really well if it checks out. Also do a pressure test on the cooling system to see if it holds pressure.

Ran for about 5 miles today. Outside temp was about 96F at the time. The temp stayed at about the 3/4 mark but would go up and down a little. If I was moving the temp would go down, if i was stopped the temp would go up. While stopped, the top hose would swell and the overflow reservoir would fill up. (Not cooling enough to trigger the thermostat?)

No oil in the overflow reservoir, no milkyness in oil (when I pull the oil stick). No check engine light. My wife started to notice it overheat around the 3/4 mark about 10 days ago and we got the van smogged last week. Passed with flying colors.

I'm hoping that "stop leak" I mentioned before is clogging up the radiator and not letting it cool quick enough.

You could pull the radiator and if you have a radiator shop nearby have them rod the core or simply replace the radiator whichever is most economical. If you find the radiator core clogged with stop leak more than likely the heater core is also and will need replaced. The question remains however what was leaking so badly that precipated what I presume was the previous owner to overdo with a quick fix.

2004 Bonne SLE
1971 Chevelle SS

Just went to pepboys and rented their coolant system pressure tester. I hooked it up and aimed for about 20psi. I over shot that and hit 22psi. I let it sit for about 5 minutes and got NO change in pressure at all. Stayed an even 22psi.

Does this rule out a blown head or intake gasket? Should I be looking at a clog somewhere? I bought a flush kit but I don't have time to do it today, I'll give it a shot tomorrow. Should I flush towards the thermostat or toward the pump (back flash? )

Alright, I decided to drive it to work today. I left early just in case I had to pull over and have my wife pick me up. Made the 6 mile drive without going over the half way mark. I took side streets because I wanted to see how it preformed in traffic. Outside temp was around 102 and I ran the A/C the whole time. Cool.
Just got off from work. Around 3am. Outside temp in the low 80'*. Didn't run the A/C. But I took the freeway home. As soon as I got onto the freeway the temp jumped up to the 3/4 mark. Never went over and never went down.
I'm honestly confused.

You might have a plugged radiator and water jackets. Happened to my 88 before the head gaskets went bad. I suggest you get a new radiator or at least try to flush this one out with a garden hose. 9/10 times flushing fixes this.

9/10 times flushing fixes this.

Disagree...more likely lower intake or head gasket......test for a head gasket leak....

I'm not disagreeing with you, about the head gasket. I'm just hoping it'* not the case. I've rebuilt my fair share of engines and i won't shy away from the task. BUT I'm in the middle of stroking the 390 in my TBird to a 445. Also, I just got the van, and this engine in sideways thing is confusing me. I haven't had a chance to really get to know this engine. Like, I'm not even sure how to change the back spark plugs. Do I need to climb under the car to get back there?

But here'* what i know:
1) i am not losing any coolant.
2) i do not have coolant in my oil
3) i do not have any oil in my coolant
4) I'm not burning any oil
5) I'm not losing any oil
6) I'm not smoking
7) my coolant system holds pressure (22psi for over 5 minutes)
no check engine light
9) passed smog after the overheating started.
10) i have not done a compression test yet.
11) i have not done a leak down test yet.

I would normally expect to show a symptom other than just overheating before i would guess a blown head gasket but i don't know this engine as well as i know other engines.

I was looking through this again, and wanted to throw some observations out there that struck me as odd.

You just got the vehicle, chances are you may have just bought someone elses problems. I hate it when that happens.
Cooling system filled with water, and a stop leak solution clumped up in the water pump housing. Water is normally used when it'* leaking so bad it'* not feasible to keep it going with actual coolant. Also I have never heard of a stop leak clumping up like that. Sure the stuff gets everywhere, but wow. Makes me wonder what they used, and how much of it did they use?
The fans were not working when you got it. Replacing a relay fixed it. It'* odd that this would be the case, unless this was the cause of the whole issue to begin with.

Also, the overheating while on the highway also causes me to suspect that either the coolant passages are clogged in the radiator, or there is an issue getting air through the radiator at speed, which could be bent fins or trash on the radiator and condenser, or even stuff piled up in between them.

At this point, I would flush the entire cooling system, really good, maybe even resorting to chemical methods. Also check for a lot of bent fins on the condenser or radiator while in there. I think in doing so you will reveal the reason the stuff was in there to begin with.