Re: .and now my rear rim is screwed up....halp
Just tightening the loose spokes isn't the way to fix a rim, You have to true it. You have to tighten spokes on the opposite side of the runout of a rim, a little at a time until the rim is straight again.
Yes spoke nipples can strip since they're only brass. Your best bet if you're unsure of how to true a rim is take it to a bike shop and have them do it. Leave the drive sprocket on since installing it puts some stress on the spokes and with it on they can take that into account when truing the rim.
I've seen people walk into my LBS with rims that were so bent I would have just pitched but after about 15 minutes in the back room and $20 they looked perfect.