As requested frame photos

You might be able to slow it down a little and buy yourself some time by cleaning it up a bit, but like @Clearwater Bill said, what you see is not representative of how bad it could be. You're not going to stop it from rusting from the inside out by throwing coats of rust inhibitors on the outside surface. Yours is worse then mine was and you saw how much bigger the patch had to be to cut that shit metal out. It doesn't need to be done tomorrow, but if you don't cut the cancer out and deal with it, you'll eventually be able to stick your fist through the hole in your frame.

Just my .02 cents.

 

Yeah, until a piece the size of a saltine cracker comes off and leaves a huge gap in the layer of sealant.

 

that ain't good. My 3rd Gen T4R is like that, I pick at those spots with a welding chipping hammer and watch iron oxide dust ( formally know as a chassis) fall onto the driveway.