I've never pulled that piece off, so I'm not 100% sure how in depth it is. Have just seen pictures of it done. The trim in your second picture has to come off. Pretty much remove the vinyl strip covering the screws, then a bunch of screws to remove. Should be a strip side to side between front cap and the underside. Then the trim around the pin box (3rd / 4th picture), and the strip across at the very bottom under the front cargo door. All of the trim can be tricky as it should have the gray butyl tape under it, which can be aggravating sometimes. Cutting any sealant first, removing screws then gently prying a little at a time and trim will usually come off. I don't have the luxury to take pictures of these pieces right now, so hopefully you see what I'm referring to. Unlike the sidewalls, that piece to remove underneath is relatively thin. But, if you can get it off, you should be able to further inspect the cross members and other structure. If you've seen the pin box flexing in relation to the cap, no doubt you have broken welds, or the steel itself is fractured / cracked as I've seen before. Cedar Creek should be able to tell you more about it than I can. I'd suggest calling opposed to emailing. I think their main number is (260) 593-2404 and the parts / service number is (260) 593-3017. Be prepared to give them the last 4 of your VIN as they may ask to see exactly what you have. You never know. I've heard of them helping out people on out of warranty fifth wheels before.
John and Rebecca Dickson
Emma-7 / Little John-5 / Iva-1
Full Timing Again, Rev B
2013 Ford F-350 Lariat CC LB PSD
2015 SOB TT - With OC's Awning Poles (#8)
At least in Heaven, RVs will be perfect, and I won't have to keep fixing them.