You probably aren't going to find a satisfactory reply to this unfortunately. Mainly because poker is situational and the above two situations are stuff that top players who have big winnner for years won't be able to give you a black and white answer. It DEPENDS.
Situation 1:
What is the player who re raised you like, does he/she do this alot if they do then folding maybe incorrect. At the lower limits alot of people are pretty crazy its just picking them out as there others who will only do this with aa/kk. What i would say is try and observe others tendancies and making an educated guess at their range, if you think they are capable of doing this with aq and aj say, you are ahead of their range and therefore making a raise/call will be correct.
Situation 2:
Trying to put someone on a set or not is one of the most difficult things in poker, IMO. In fact whenever I see a set shown in game or when I go through my database I will note exactly how they played the set. Did they bet, did they check raise if so how much, did they wait till the turn to make a raise.
If you want a general guide players at the lower levels love this line, example
Your hand :

His hand :

Flop:

You bet they call. Turn blank you bet, they min raise. OR if they out of position will check to you then raise the turn.