1.) You should call if ur getting 4:1 on your money or better.
2.) Not sure honestly. I think it could go either way. You could bet pot, but you're making it so only better hands call/raise and worse hands fold. On the other hand, if your opponent folds 1/3 of the time you break even (i think) so like i said 50/50 for me.
3.) Depends on if you feel like gambling. You're about a 50% to win so if you feel like risking your stack on a coin flip call, if not, fold.