late to the show here - but my 2 cents.
glad someone else brought up 1192. no, thats not code, probably not in Canada either. and just personally, i've never seen propane lines in other than the standard black pipe, copper, or the newer pvc thats rated for it. idk what its called, though.
1192 is a quick read when you find it, and will tell you what is safe and where it should be located.
worse and more likely than an exploding grenade, is just death. leaking rv fridges are responsible for plenty of them. yes, you can explode, but more likely you'll fall asleep and not wake up. leaking propane displaces the o2 in the rig and consumers suffocate in the night.
those risks led me to stay away from propane completely.
the 5lb bottle may or may not push the propane, like that, i've certainly experienced that myself with a floor heater that draws too much. they ice up and freeze. the solution was a 100lb bottle.
if it were me, id run a single line of black pipe to the water heater with a t just before for the stove. then a short flex to cnnect each appliance.
making it temp is tougher. maybe just a flex to a bulkhead on the side of the vehicle and then your bottle how ever you like.
propane leaks, regulators are designed to leak when they need to. mounting the tanks and lines so high, is questionable, since and waste propane will only travel down, possibly into your living quarters.
wish i could say "send it", but would rather you be safe than sorry.