Given that you think this is a tight player (or at least that is where your information is leading you to believe) I am not going to 3bet jam him very light. There is no reason to believe at this point that he is opening anything outside of his tight range. I disagree with your thought on flatting here, you have <20bb's. There are only 2 ways I am playing a hand here

1. Fold

2. Shove

That being said from here against this UTG raiser I am probably doing this with JJ+, AK+. As I develop more specific information this range will adjust accordingly. For your second question, you should be jamming very strong, but from this position with that chip stack I am going to call with my opening range. I can't really see folding a 20bb stack opening UTG, this is what I am looking for, someone to spaz and jam into me. My guess is that with this stack size for a tight player you are looking at QQ+, AKs, maybe AQs, KQs, but that is about it. I don't think you are going to get lucky and see a TT or something like that in there very often. The other thing to consider about his range here is that he is opening and there are a bunch of short stacks to act after him in the 10-30bb range, so he can't be terribly afraid of playing for his whole stack here. Makes me wary when they do this.