I guess when my control arm let go, it took the cv boot with it. The boot is still on, but it'* definitely torn pretty good.

How long can I drive like this before it needs replacing/how dangerous is it?

I'm asking because my next day off is Tuesday, which is when I'm going to install a new axle. Until then, it'* either drive it with a torn boot or don't drive at all. : /

You can quick boot it if you are worried about it, but I have heard many instances of people driving on torn boots for a long time. If you are going to put in new axle tuesday, assuming the cv joint didnt come apart, i wouldnt think twice about driving it until then. Just be wary of excessive speeds.

maybe put some duct tape around the boot to kep the grease in.

It'* going to sling grease, but should be fine for a while. Once water gets in there it will start to wear and get sloppy.