Originaly I wanted to look through the hand to see if I do have value bet OTR, but I started to assign ranges and kinda questioning now if betting OTT should be a 'go-to play' at all.

so, SB is fishy 38\3 only 40 hands.

PJ ranges.
preflop range: $FI30!3bo4

OTF: J+,QT+,8T+:2+,Tdd+,dd:9+,QQ+:QK+,78T+,QQ+:hh ! JJ,J9+:Kdd+,J+QT+):Add


so, OTT he pretty much shouldn't have a raising range, as for calling sub-ranges I put:
J+2+,8T+,dd),Qdd+,dd+:5+,QQ+:QK+,9+:34+,346+,25+

dunno, maybe 25+ is a bit optimistic(?), but anyway.
Range Distibution OTT shows that he has like 96% of calling OTT (only <4% folds), so if it's anywhere close to be trues - we pretty much don't have FE.
then vs this calling sub-range we have (only) 53.5% of equity.
and OTR there will be K\Q\A, even T and diamonds that are tought to play in
bigger pot. (escpecialy in case if he has some bluffs OTR)

You pretty much answered your question.
We can't bet here if we can't protect our hand and have no value. Also you rarely will be bluffed out of better hand on the blank river to make free SD bet.
Turn changed nothing that's why you have little FE.

As played - clear river bet since fishy unknown will bet any better hand by himself more often then not.

Whenever you have 4% FE in a spot like this, one of two things is probably more relevant: 1) opponent is bad, 2) assigned ranges are inaccurate in places.

Both seem to be the case here. Wrt #2, that flop calling range can be widened at least slightly, both made hands and draws.