What relays would you check? I'm assuming the fuel pump relay is good as the
fuel delivery test worked fine. Others?

The curious thing, again, is the gradual deterioration of starting, from "un
quart de tour" as the French say, to many revolutions, to no start.

No evidence I can see of internal engine problems--no smoke, white or blue;
 no oil burning;  no water in oil or oil in coolant; normal power. But you
never know. I guess a leak-down would be a next step. But would bad
compression keep it from starting?