Your question about wasting your time….. Absolutely not. My 1958 5hp spent its early life in salt water then sat unused for 40 years.
A couple years ago a carb cleaning, ignition rebuild, fuel pump and impeller service brought it back to life. It starts easy, runs smooth all day.
A compression check before resurrection was also 65lbs! I thought I was wasting my time too but remembered it ran great when I was using it in the 70’s and it didn’t dissapoint.
You will be all set when you find that last bug.
I run 16:1. Kinda fun to experiment with oils to see which smoke etc. and this spring it really liked the rediculously expensive XD100.