Rust at pickup bed bulkhead, thoughts?

So, after my 1st gen was totaled, due to the lack of reasonably-priced, solid-framed 1st gens in my area, I ended up picking up a 2010 Ranger. Externally, it's rust-free and the frame is brand new looking. I've already utilized the knowledge gained here at TW and Fluid-Filmed the shit out of the entire undercarriage and every nook and cranny. Unfortunately, the previous owner had a factory bedliner in, and apparently never bothered to take it out and clean periodically. When I pulled it up, there was a layer of silt and rotten leaves up at the bulkhead. Have I mentioned how much I hate these plastic bedliners yet? Looks like the line-x I had planned isn't going to be an option without doing some bodywork, and I think based on the location it's going to be hard to really clean these ridges up. Honestly, I hate to admit it, but I'm thinking about basically hosing down the entire floor of the truck with Fluid Film, going especially thick at the bulkhead seam, and then just throwing the damn plastic pos bedliner back in and pretending like I didn't see this. What do you all think? The metal isn't squishy or anything, but I know it's going to get worse quickly if I just leave it uncovered and let rain/snow get into that seam.

 

I would go to the car wash and blast all dirt and lose rust out, then hit with a rust inhibitor.