Wow,
Thats a lot of questions!
I'll try and answer what I can:
#1 - Yes, all back inflation BC's and wings tend to push one face-into the water. One merely needs to flip over on their backs to swim, or remain floating at the surface.
#2. I use about the same weight that I used for jacket inflation.
#3. I found the back inflation kept me at a nice horizontal plane in the water, and not in a feet-down position at all.
#4. Yes, it responded VERY well to inflation / deflation.
#5. Yes, with MY mask on, I can't even see the D-rings on the shoulders.
#6. I have no idea. After the dive, they were in the fully extended position. I have a copy of the Mares owners manual in Adobe PDF file if you would like it e-mailed to you (may be too large) or you can go to Mares web site and download a FREE copy of it for the BC for yourself as well. Haven't really read about those yet.
Note: Its is a heavy BC, but once you hit the water, I didn't even know it was on. It was very comfortable out of the water, adjusted easily and well. Zippered pockets were nice since I put a waterproof Otter Box in them to hold our car keys and money for air fills. Mares sports nice LP hose holders, but I use mostly SS Bolt Snaps on my SPG.
The integrated weight adjustment system works great. No problems there - very secure with large ergonomic handles to release the weights - if ever necessary.
All in all, I can quite happy with my BC - fits very well and I like it. By my 2nd dive, I had my trim and weight figured all out and was neutrally buoyant as well and had a great dive.