I can only answer one question and thats for the mystery screws. More than likely, they didn't come out of anything and were left over from construction. May have rolled out from under something. I've found quite the collection, plus some other things during removal of vents, panels and creating access panels. The more panels and compartments you open, the more items you'll probably find. Probably find a bit of sawdust and wire pieces too. Hold onto the screws, you may need them for something later.
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.