Yep, the one behind the door is the b pillar. At best you are going to have to loosen everything. However, getting everything ready to be loosened is the hard part. The hardest part is getting the body rubber/adhesive off the cage plates on the b pillar. Invest in a set of mechanic picks (they look like dentist tools), utility knife, and windshield sticker scraper. It will make getting that stuff off a lot easier.
if you go through the trouble of getting the bolts loosened, you might as well go through the rest of the hassle to just take the cage out and do a good job in taking care of the rust.
Also, get some PB Blaster, a hand drive impact wrench, a good set of torx bits (believe it or not, Stanley's torx bits are really good; they out performed some high end torx bits that I had. I picked a set up from Walmart.) and some stuff called Freeze Off. It will make the project much easier for you and save you some time!
The cage itself isn't very heavy; you and a buddy (or two) can lift it out if you choose to take it out. You may not have to take it because you can probably prop it up enough to do what you need to do. While you are at it, I would go ahead and replace the torx bolts with standard bolts that you can use a socket on (chances are, you will strip a few of the torx bolts while getting them out).
Check out Monstaliner's web site and look into their "chassis saver" as an option as to what to cover the rusted spots and/or to prevent rust in the future. You can paint over it and the stuff is solid! The use the stuff on naval ships as a rust preventative. I coated the inside of my tub with it before I rolled the Monstaliner bedliner in and coated a cargo rack with it! It's great stuff, it's inexpensive, and speak with Eric Rosenthal because he is great to deal with; you can't go wrong with it!
Hope all that helps and gives you an idea of what to expect and opens some options for you!
Sorry it took so long to respond, I thought I had my settings to automatically subscribe to threads I replied to (wasn't the case but is now!).