New 5th wheel purchase. I think we have a lemon, need advice

"You can not blame the MFG for what you didn't do, it's all on you now, as someone said good luck but I'm sure you have bought yourself a bag of worms an it will cost you dearly for your hast ..."

Actually yes you can blame the MFG for issues like this. If the trailer were built correctly the PDI would only be a formality, not a necessity. Most of the issues should have been caught during the PDI, but in reality they shouldn't have even been there to be found.