Lol, asking me further questions is probably just wandering further down the garden path.
Freeroll, so could be anything really, but limp utg can be big hand looking for a raiser to pounce on, which he doesn't, or a solid hand looking to flat a raise, which he does, or a speculative hand that doesn't fold to a small bet.
Assuming he's close to a starting stack, then he is probably nitty, so AQ, AK 10,10+ KQs ; J10s+ as you say or a small pair likely. Because he is a nit, he has part of this flop, but your small bet prices in his full continue range. He doesn't ck back turn, though his bet is small. Some player might limp a weak ace and call a small bet, and make small bet on turn, but not usually a nit, only a tit.