My first hand at the table. No reads

I post in CO with a full stack. [8c]

UTG ($44.50) limps, MP2 limps, I check, SB calls, BB checks....5 to the flop

[Jc][7d] Pot $2.50
SB and BB check, UTG bets $1.50, MP2 calls, I make a marginal call, Blinds fold

Pot $7
UTG bets $4.50, MP2 folds, I call.
Thoughts: The 8 didn't seem to scare him. Right now I'm trying to figure whether he limped with the intention of re-raising with AA/KK and is trying to make up for it. This is about all I can beat.
Or he has a straight or even a boat which I can't beat.

Pot $16
UTG bets $12, I ???
Thoughts: He still hasn't shown fear of the paired board. Fold, call, or raise?



Hand 2: Same table, exactly 1 orbit later. I have [8s] in CO. No read on SB. He has $52, I have him covered.

UTG+2 limps, MP1 calls, I call, SB raises to $3, 3 folds, I'm last to act so I call

[Ad][8c] Pot $7.50
SB checks, I check
Thoughts: If everyone had called, I could see a check meaning KK or some hand that is scared of the Ace. With only myself to act, I would think that he would bet with the Ace out there. I fear that the check means strength here.

Pot $7.50
SB bets $2, I call
Thoughts: Is this a great card for me or a disaster? Am I right to fear AA here? He'll throw away KK if I raise, no?

Pot $11.50
SB bets $7.50, I ???