After raising this flop, I'm barreling any turn (100%) & most likely the river. My logic being I want to get paid when I hit. I may give-up with some reads. With little/no info I am barreling this, the river is a little closer but still a lot of draws bricked off so if I did bet the river here, it would be a smaller bet.

during the hand, i froze when the board paired. i clearly didn't plan things out properly. i like a turn barrel since villain's range is likely wide:

1. what is my turn barrel sizing?

2. if i did get raised OTT am i folding? feels gross but outs are no longer clear

Your 78hh blocks some of villain's drawing hands so there may be a better candidate to bluff (if that's what you're going with) with on the river - perhaps some broadways that block QJ, KJ, AJ or JT. I agree with dynosaur that barrelling most (if not all turns) is necessary if we want to get it in on the river when we hit.

But if villain is playing as many hands as you mention, although he may have suited and connectedness in draws that dominate you, he will also have things like KT, Q9, T9, J8, QT, 98 (and 77 - AA are all likely to be in there also given his passive nature - lots of which are not folding once the turn comes). So if you do barrel the turn - you are going to be stuck checking to him when you miss a lot especially if he likes to go to Showdowntown (how likely are his TT and K9 to fold to a river bet?)

I'm still not entirely sure what the best play is vs. this guy.

I think there may be some merit to the X/C line you took vs. this guy and perhaps donking out when hit to get his marginal showdown to call. He bet 1/4 pot and then 1/5 pot, which feels like a weak-kickered Jx or a TT, 88 or 9x kind of hand (and slow-played boats). If the flush or a T hits you could donk in to him, and raise his bet if a 5 peels. 

If he raises it puts you in a gross spot, but after seeing the K6o limp, that seriously dilutes his value, especially if his WTSD is high.

Still unsure.