great spot to barrel just remember you don't have to bet very much. 30-40% of the pot is more then enough. also just curious what do u mean he bought in 10K but took 5K off? are u trying to say he's down 5K or he actually took chips off the table? (that's called going south and is against the rules).

He probably means he gave a runner 10K and stuck 5 1K chips in his pocket before playing a hand (legal) it's not super relevant but you could use it to aid some assumptions.

defo a bet he's got a lot of 1P+sd type hands/hands like our which he'll fold a lot of the time. He has 42 and 72 (and 44 and 77 but not as often as you) so your range is stronger combined with the fact you got bucket loads of equity vs everything that isn't the stone top of his range. Agree w/RBK can go a lil smaller but I wouldn't go as small as 30/40% would stick around half pot for a live poker game (i'd be betting $180/$200 online) but I think you need to go a little bigger live for same FE (people are a bit more stubborn in live games, imo)

would be value-betting our rivers for sure as well

I think its fine to play the flop that way...I wouldn't c/r on that flush board without a FD to go with the wrap. More importantly from HJ, ure only hope to bet is the button and kinda looks fishy taking a C/R line like that. So bet and thin the field so u can make a decision on based on turns.

 In this turns case I think mostly likely you can go ahead and bet that turn, you don't have much info on the guy but u know he is aggressive with his solid draws and protects his made hands, so he is mostly likely gonna protect that draw heavy board if he had a set of sorts. I would little over half pot the turn, and  bet about 70 % on all non-club rivers whether or not my straight gets there.