This hand, I was 99% sure he flopped a set, and not just because of his line, but he said, "I love it when that happens." Obviously referring to getting raised when he spikes a set. If I am pretty sure he has a set, is this just a fold?

PokerStars No-Limit Hold'em, $0.25 BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

MP ($27.20)
CO ($23.80)
Button ($37.55)
SB ($24.95)
Hero ($27.60)
UTG ($19.85)

Preflop: Hero is BB with J, Q.
2 folds, CO raises to $1, 2 folds, Hero calls $0.75.

Flop: ($2.10) 5, 7, 8 (2 players)
Hero checks, CO bets $2, Hero raises to $6, CO raises to $18, Hero raises to $26.6, CO calls $4.80 (All-In).

Turn: ($47.70) Q (2 players, 1 all-in)

River: ($47.70) A (2 players, 1 all-in)

Final Pot: $47.70

In this situation, is just calling him down okay, no real reads on him, but i figure just a King is good here a lot.

PokerStars No-Limit Hold'em, $0.25 BB (5 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver Cards)

UTG ($19.45)
Hero ($41.75)
Button ($16.70)
SB ($13.35)
BB ($31.45)

Preflop: Hero is MP with , .
UTG calls $0.25, Hero raises to $1.25, 3 folds, UTG calls $1.

Flop: ($2.85) , , (2 players)
UTG bets $1.25, Hero calls $1.25.

Turn: ($5.35) (2 players)
UTG bets $2.25, Hero calls $2.25.

River: ($9.85) (2 players)

UTG bets 3.75, will641...

Final Pot: $9.85