PPpoker 6 max online 100-200 baht (comparable to 3-6usd)

Villain 1 UTG raise 600 (29590 effective) (donk raising utg pretty liberally)
Villain 2 HJ call 600 (65800 effective)
Villain 3 CO 3 bet 2400 (90100 effective) (solid good player)
Hero SB 4 bet 7200 AsKs (24610 effective)

Folds around to Villain 3 who flats.

FLOP 2h7h4c
Hero bets 5500 (leaving 11,910)
Villain flats

TURN Qs
Hero checks
Villain checks

River 2c
Hero checks
Villain shoves all-in
Hero folds

Question:
1) Was 4 betting there too light and was bet sizing too big?
2) When he calls should we be checking our frequency more than betting realizing he has a lot of op he is not going to fold?
3) Should I have shoved the flop instead with the awkward chip stack?
4) When he flats the flop should I just get it in on the turn with a little less than half pot remaining? (Figured there was not much fold equity)

Thanks for any advice in advance!