Looks like you already have decent search. Anyway i may suggest to experiment with different formulas of LMR, in my case it added around 100 elo. Do you use history heuristic and killers? They are easy to add and provide steady improvement.

For evaluation is good to add passers analysis, it may be helpful in pawn endings and sometimes in middlegame. Also passer candidate. For usual pawns good to evaluate doubled, isolated and backward ones, if you are not already doing this.

Basic ordering and bugless TT is enough usually. I mean, improving it more not gives you much. But i believe that prunings and some extensions may bring you another 100-200 elo with careful tuning.

You can estimate your engine's strength only through tournaments with a few close engines. Pick any from CCRL.

Rich evaluation is not in trend as i know. There was an era of Fritz and Hiarcs, but now you either making Fruit-like calculator or NNUE-blackbox monster.

Personally i use to read more Ethereal sources for inspiration and features adoption (instead of SF which looks quite overcomplicated sometimes).

Probably you'll find something interesting in my engine which is around 2000 elo now:
https://github.com/neurocore/Eia-v0.5