When you replace the plugs check out the terminal connector inside the spark plug wires. Also check the connectors on the distributor side of the cable. While you’re there also check the contacts inside the distributor.
As for the STA-BIL, it cleared up my issue with rough cranking. With all the posts on ethanol issues and it destroying marine fuel systems I decided to start treating the gas. I live in NC and some stations have less ethanol than others. I try to find stations with a lower amount but they all have it