Congrats on figuring out how to make going turtle work. It is a challenge.

Guns and reloading are always an issue. One novel press solution is the Huntington Die Specialty (HDS) Pack tool.
As far as safe storage goes, as well as possession of certain firearms/magazines, it is sticky. While we may not appreciate various local laws, one canot ignore them either. Especially if we live in the state in question.
Californias ban on almost anything useful does have an advantage, being in compliance there means you are in compliance pretty much everywhere else. Figure out how to secure your s5uff without a safe, it can be done, locking cabinets for example.

As to the cops, their question is worth a look.
One, their own safety after a low speed incident involving a weapon.
Secondly, they were trying to determine your rank, scumbag or good guy.
Thirddly, there is a jurisdictional issue, the little M4 I keep behind the seat and its magazines would get me in serious trouble in some states. Guns with certain compliance features are worth the time to avoid hassles.

Make sure you are in compliance with federal laws for/while traveling for safw storage as well as travelling through certain areas, national parks are particularly sticky. The other issue is CCw. Without a permit, that cubby for your .45 is trouble. Unless its empty and useless, and locked up. That rv may be your castle, but it has license plates and while mobile still is considered like a car in many respects.

There has been any number of mobile meth labs, and dope deliveries made using an rv. The family is cover, to hide the dope. And like it or not, a 40ish couple with kids does not normally go turtle. It attracts attention.

A thought, get yourself a small plot of land with an address, to make your “home”. Register your vehicle there, get new drivers licenses and CCw permits. Because of what you need, it doesn’t have to be complicated, just a parking space with power. Any number of small abandoned farms fit the bill. Check around as you travel. There is a difference between someone with no fixed abode, and a landowner on vacation (nut on a family quest).
Even if that plot is just in a more CCW friendly area that will give out a statewide CCW, that is still valid statewide.

Personally, a CA compliant arsenal still isn’t a bad chiice, me I’d be looking at things like an AR-180 (original) as its pre ban everywhere and should fall under the grandfather clauses, after all who’s to say how long you’ve had it. A rebuilt/refreshed M1 Garand also bears a look. An Ithaca 37 Deerslayer for hunting deer and hogs also makes a great defense gun, LAPD used them for decades. And no ban bs on them.
Handguns, a little more sticky thanks to the registration laws, but if your plot of land was in Wyoming, you could travel with certain of your non compliant guns provided you kept low cap mags handy for use there. Since you wouldn’t be importing them, just travelling.

I know of one traveller who keeps three guns handy, one a 1911 because it was his fathers. Legal everywhere thanks to low capacity and age. His daily carry gun, a Glock 26 9mm. Modern yet low caoacity. His third? Another Glock 9mm, an early Gen 2 gun with low capacity mags. His reasoning behind these?
Modern enough to be abuse and neglect resistent, parts and mags are everywhere, even the neutered mags. Simple enough that even a cop knows how to operate them in case something bad happens.

He regularly visits CA, family there but he keeps a couple of ammo cans near the border, cached. Inside a number of Glock magazines, he stops for a rest before entering CA, and swaps out his good high cap mags for low cap models amd leaves the hi cap mags in safety out of state.

His rifle? A Ruger Mini Thirty with a bag of 5 round mags, no evil features and he uses it to hunt hogs. As such its set up for close range fighting, minus the hi cap mags, also left in the ammo can.

He’s considering switching to an early G23 but isn’t sure how frame replacement later may effect him with the CA laws. Since the gun would no longer be pre-ban technically.

A survival author/speaker Brian Brawdy did something similar to you and your motorhome, his work may be worth searching out.
Good luck..