1) What range do you put villain on by the river? What portion of that do you think he'll fold? I think the river barrel is good as there are hands that he will call flop that will fold turn. I think I give up river even though this hand has good blockers for good Kx as it's hard to find hands that villain calls turn to fold river on this run out.

2) I think you have to 3bet bigger preflop, you should be looking to make it around 3x the open when you're in position and 3.5-4x when out of position. I also think this is a bit too thin to bet 3 way on the flop in a 3bet pot. On the turn when you get minraised I'm not loving the spot but I think call is by far the best option. Shoving isolates you against worse most of the time and folding is out of the question. On the river I think you can decide based on sizing and the run out between call or fold.

3) I think the flop sizing is a little on the small side, just a bit bigger would be fine. The turn lead is really weird given that the only hand it should improve is A6s and that's only 1 combo. I would probably call turn and call most rivers. As far as a video on sizing I would recommend Intro Into Bet Sizing by Steve Paul

Hope this helps!