Im doing almost the same, i call it the 'prepper challenge', the same problem, fire in the houses i have close and end... just disable the fire spread in sandbox and solved.
You are still in danger of a direct hit... but thats fair i think.

If we speak about playing without disabling fire spread / airstrikes, you can make a few stashes in different basements. It depends on the type of the basement of course, but this method helped me, bc my main basement got bombed and started burning and I ran into the one in the neighbouring house. Mark a few houses which have basements on the map and stash supplies there.

It depends on the basement type ofc, because I had those that have the entrance outside of the house and entering it doesn't count as a trespassing. The one I used as my second shelter has a garage above but by the time I went there, it was already complete chaos.

I also had an issue where my third basement which I initially marked got infiltrated and barricaded by people from the inside, lol.