PO Boxes through the Post Office do require local residency. PMB do not… Private Mail Boxes. You can get them at the little copy/mail shops all over the US.
I have a “prepper” minded family member that has several 24/7 storage lockers all over the US. Many places you get to go are a bit off the beaten path so prices tend to be rediculously low for some things. He gets the smallest available and I can’t imagine it being too spendy if you shop around. Several of these placed along with caches and such could allow you to have supplies (including a cheap Mosin or such rifle) within a day’s drive.
I couldn’t handle not being able to at least have a firearm in a rucksack even in a disassembled state. I actually have an AR7 Explorer that stays in my truck all disassembled and in different spots so I can’t be messed with by overzealous LEO’s. Not sure how something like that would work for you, but it would be be better than nothing…. .22LR hurts if shot with it. Just saying.