Is the breaker tripping from an overload, or is the GFCI tripping because of a ground fault. It sounds like it's just a simple overload if you were able to set the fridge onf LP and removing that load solved the problem. A coffee maker is quite a high load which is why home kitchen outlets are now required to have dedicated breakers to each outlet. I would just set your fridge on propane, leave it there, and stop overloading your circuits. If you have other outlets on other breakers that you can use, spread the loads among them.
Brian