Re: Rust repair
The rear door cannot or should be not repaired---existing rust is just too severe to even consider. Find a good or near-perfect door for replacement. Yes it will require refinishing to mostly match the rest of the van but you don't see such things from the driver's seat.
Upper right side gutter---needs to be addressed ASAP, possibly removing the plastic trim material for further investigation. At that angle of view its tough to know how extensive it really is but given its location and potential for bigger issues attending to it soon would be advisable.
Right side lower rust----the doors are deteriorating much like the right side rear door, they're pretty much in-line to be replaced as well. While they could be surface repaired the rust has begun inside the door shell and can't be stopped to any high degree of success at this point. (Just a bundle of good news huh?
The lower B-Pillar rust looks to not yet perforated the metal, rust most likely having began from a small rock chip in the paint that exposed the bare metal to the elements. We'd want to see other single views of that area with front and side doors open showing the pillar where it joins the lower rocker panels. Also crawl under the van checking that area to see if rust has found its way there.
FWIW I'm a former body shop owner who has a bit of knowledge with rust repair, might be able to share some useful info.