You're making the adjustment way too complicated.
All you need to do is take the wheel off, leave the drum on, and behind the backing plate you will find a slot that should have a rubber plug in it, it may be gone. Stick a flat (regular) screwdriver in the slot, and I can't remember if you pry up or down, but one direction will turn the toothed adjuster and spread the shoes out to touch the drum. You want the shoes to just touch the drum so when you spin the wheel, it still turns freely, but you'll hear it scraping on the shoes. You don't want it too tight, or you'll overheat the brakes and lower your mileage.
I've looked into swapping rear discs in too, and there'* not a simple swap in. There are kits you can buy, but they're very expensive. ($1300?) It'* not worth it, and the rear brakes are not the reason your rotors are warping. Rear discs wouldn't solve that problem.
1996 Olds LS, 198,900 miles: RIP...