#1. It is called a control arm. It is usually referred to as the rear control arm. There's actually another control arm just a few inches in front of it, that's sometimes referred to as the forward control arm.
#2. I suppose the correct answer would be to replace it with a new one. However, I straightened mine without heating it. I had the same problem you are describing...both arms were bent like crazy. I removed the control arms, placed them on a metal vise, and beat and banged with large hammers until I finally got them into a nearly perfect condition.
#3. If you want the alignment to be correct, you'll probably need an alignment. I suppose that if the alignment was perfect before the control arms were bent, and if you restore the arms to their original condition, the alignment should also be correct. However, that's a lot of 'ifs'. The only thing we can adjust on these cars is the toe-in, which is a fairly straightforward adjustment.
Good luck.