listing SBvSteal for 425 hands is silly. he was in position maybe 6 times and called once. More important is the BB (high sq? a fish?) and the stack depth which are both key factors for estimating his calling range there preflop.
Flop cbet is standard, checking back can work as well though vs a loose defender.
Turn is somewhat close. You have a very good gutshot, some solid top pair outs and 3 more outs to the six which give you at least some showdown value. So barreling is certainly reasonable. You do however also have all possible overcards, which are similar in barrel-ability, and you certainly dont want to 2barrel all overcards+fd+A6. So your check seems fine, but it's close enough that a read can make all the difference.
River. Due to the lack of 6x in his range (6x doesnt call from the SB, 65 76 check raises flop often, and if he rivers it he will bet himself sometimes), I think overbetting with your 6 is good. I'm not sure if the sizing is optimal, it seems a little bit too big, but it's ok.
When he raises allin he will never be bluffing (unless he is bad crazy). So you are looking at 6x with which he is semi bluffing (trying to make you fold a split) or 76. 76s in any suit can check call flop + check raise river. So I think you have to give him credit for more than just 1 possible 76dd combo.
Assuming he has 6x or 76, you are risking ~$100 to win ~$30. So you need to be right almost 80% of the time. If we say 2 combos of 76s then you need 8 combos of 6x. 66 comes to mind, maybe 65s 64s 86s. It's difficult to tell how often he check-overjams river with 66 instead of just check minraising or even check calling. It is certainly possible that he is semi-bluffing often enough.
My personal read would be that people don't check-overjam with 6x to fold a chop often enough, they will be more worried about getting value than balancing their check-overjam range. So I think I would make a tight fold. But calling is certainly fine.
A 
8 