There is a lot of information missing; how the two players have been playing, how the table has been playing, etc. Given that it's a freeroll I guess you could assume everyone is clueless.

KJ at a full table is an easy fold pre-flop. If the table is passive and bad limping is OK I guess. A raise to 600 is ideal, I guess 500 isn't terrible. Checking to the pre-flop raiser is standard. Flop bet is fine, he's left with PSB and sending the message that he's playing for stacks, which he is. Push over this bet, don't call. Turn plays itself.

Percival, your raising range is way to tight, otherwise fine.