I bought 3 commercial grade "fob" devices and all were pretty bad. I wonder if you might be better off piecing your build together with a commercial grade fob unit controlling a more robust marine relay that you purchase and install separately.
and it is pretty cheap. With any load on it it isn't reliable, but I have the device sealed into my own project box with a Bosch waterproof relay kit. Basically all the heavy lifting is done by the Bosch relay, the fob only need to run the switching current not the actual load. In that setup it has been out in the rain and weather for 2 years with lots of cycles without failure.
My advice is to find a fob system you like and pair it with a relay you trust.