#1. My curtains and sidewalls have never gotten wet while traveling in the rain. That said, if the side of the TM is wet while taking down, the front shell curtains will get wet (and dirty) as it rubs up against the back shell. We try to wipedown the back shell as much as possible before closing up when wet, including the roof that goes in between the shells when folded. Dust might be a little more of a problem then with a traditional TT.
#2. After checking to make sure your exterior black water valve is closed, you can pull the inside valve right before you close the TM. At the dump station, open the exterior toilet valve, close, then pull the gray water valve to help flush the line. Remember to close the interior toilet valve when you get home. I have had to raise the TM a couple of times at the dump station when I forgot to open the interior valve....but that doesn't take but a minute or 2 more.
The beds have plenty of support (I believe they are rated @ 600 lbs. ????). You have to be somewhat careful when you push the beds in to keep them straight, but that is a minor issue with us. But 1 very important thing: Always make sure the beds are "locked in" before using them. The beds swivel up for your emergency exit, and too much weight on the back side without locking in might land you on the ground below.
Haven't experienced that yet.
We looked at hybrids also. The main thing we didn't like was the towing height, and usually you have to make the beds when you open the ends. We leave the beds made in the TM, although sans pillows and thick comforters......too close of a clearance between the shells for those. I imagine there is not much time difference between setting up a TM and setting up the beds in a hybrid.
Chap