[handparty]

Hand 1 - did he think your smallish bet then check was evidence of weakness? I've got the feeling he might be bluffing or semi-bluffing (partly based on his betting in later hands) but 400 is perhaps too big to call. A post-turn bet of 200 might've been better.

Hand 2 - Again I think you're ahead, though not as confident this time.

Given you were able to take him out later in better spots, I think your folds were justified. It's usually best to try & not get involved in big pots unless you're confident you're ahead.