Welcome, Trish!
(1) It's not carpet. It's marine-grade headliner. Mold should not be an issue as long as you ventilate during a shower and dry down after, which is SOP in any wet bath.
(2) The front bath has about 5" more headroom in the shower pan and more space overall. At 6'1" he will still have to stoop, though. I believe some people shower sitting down in the side bath. It's pretty tiny.
(3) That is debated. The deluxe models do tend to weigh a little more, maybe 100-200 pounds, but they also have more cabinets and storage, aa well as more standard equipment.
There is one deluxe (and several standards) in the "Trailer Weights in the Real World" database. It's the first thread in the General Chat section- post #297 links to a spreadsheet of the data. Very helpful when trailer shopping because these are loaded-for-camping weights, not misleading dry weights (that don't include options, batteries,
propane, water, or any of your stuff).
Not
weight related, but deluxe models also have a wider bed (54" versus 45" in the standard). The side dinette, front bath deluxe layout has an odd, cantilevered galley that leaves the stove partly hanging over the dinette. Haven't seen it in person, but the idea is a turn-off for me.
(4) If you don't get any offers here,
Scamp has a referral program that connects potential buyers with local owners for demos. Their sales department can set you up.
Best wishes!