When filling the gas tank, I also add a stabilizer. I run it for 5 minutes or so to get the stabilizer up to the injectors. Then I do not run the car until Spring. I too put on a battery trickle charger.
I just fill my car with gas and park it for the winter [or in the case of my winter Reatta, for the summer]. I don't fire it up, but I do disconnect the battery.
If it has the Magnavox ignition, the original single coil block style, try closing up the spark plug gap to something in the .042"-.048" range. If it is a misfire under load, that may help. Incidentally, I just run Autolite copper core plugs, my preferred type from way back, but then again, I actually change whole engines somewhat regularly🙄