I'd 3 bet all day long for value with this hand sb vs BU, he'll continue wih dominated hands, getting him to fold some J9s or 55 is also a good result since we're oop and have no postflop reads.

This turn is a seriously easy bet vs an unknown you're just letting him check back worse pairs and weak kings, go for 3 streets of value here all day long.

As played you can't fold the turn no. He has few combos of better hands and likely a ton of worse kings or floats.

Is the 19BI downswing defo just a result of running badly? Maybe drop down and work on your game for a while if it's affecting you enough to doubt standard spots like betting this turn vs an unknown.