You're both stuck on the different sides of the same coin:
- Family & Weather
The only real difference being that you're established where you currently live. (great schools, working businesses, etc.)
I wonder... because you say he's prone to depression if things have just gotten too "calm" after the chaos of recent years. The kids are all in school and doing well at last. Your businesses are up and running. Your mom is in remission... so instead of enjoying a moment of peace... he wants to chaotic things up? (Super common with certain types of depression. The chaos seeking... which the adrenaline and the stress "self medicates" part of the depression).
If he's chaos seeking do NOT NOT NOT move... or you'll be moving every single time you guys get on your feet. Chaos seeking needs therapy and possibly meds. It's a sign that the brain is SERIOUSLY missing some chemicals in it's everyday functionality AND that some reeeeally unhealthy coping mechanisms are at play (similar to drinking away the pain... you always end up back at square 1).
If he's just miserable because of the weather (I can soooo empathize, as I bet, can you)... the compromise MY family used might work with ya:
We summered.
No matter where we were in the world (military) we summered in Seattle. The week after school let out, to the week before school went back in session. Granted, back then (I'm not that old) it was 12 weeks of summer, so we got 10 weeks in Seattle.
I was VERY close with my grandparents... but that was the "only" time I saw them. If you add up 10 weeks... that's 70 days... which adds up to once or twice a week spread out throughout the entire year. Add in phonecalls? Skype or Facetime? (didn't even have those when I was a kid) and staying tight knit is no biggie.
You can probably work your business to do summer shoots in TN, so still be bringing in money... kiddos get gramma time. NO idea what your husband does... but he may even be able to have 2 offices if you split your time up in TN. Or if not... if he busts his bum one week, and drives up for the next (or flies, some commuter flights are super cheap) he could go back and forth.
All this depends on a lot of other factors clicking (like really good schools, and FL is known for pretty terrible schools, but of course, there are good individual ones), being able to set up your buisnesses in FL, etc.
It's just a thought. In the 'have your cake and eat it, too" variety.