I bet there are things you can do together.Remember they don't do anything they don't want to.If he didn't want
to spend time with you he wouldn't.Take a trip to Okla.City surprise him with the FFs museum and theres a bunch more to do.
I too am involved in FF and it hurt my marriage,being chief I felt like I needed to be around more,my X became an EMT and is on the dept. now
Hang in there you will conquer.