The ideal solution for you would be solar, and lithium batteries, but that's a lot of money up front. It would solve all your problems, though, and likely outlive the van.
200Ah of LiFePo would give you about 140 useable Ah's, at about half the size and about a quarter to a third of the weight as those agm's. And no need to keep fully charged... in fact they prefer to stay in the 20-90% soc range. No top charging, no EQ'ing, a higher, flatter voltage curve (meaning way less voltage drop under load), and so on.
280 watts (2 x 140w) of pwm solar would keep them up nicely. That would require about 5' by 4.5' of roof space.
Pair all that with a decent psw inverter, and you can do pretty much anything you want.