3. The LeftAlt one, Q and E work fine.
6. It seems as if the cursor and the item you're holding are misaligned in the inventory, so you'd need to have the cursor outside the window to place items on the corner.
7. No, I didn't. I believe it's best if you leave it with the tighter grip as the default as it's something that won't do anything but improve the experience.
11. The problem is that you may leave the crouching position as you walk forward looking around, and not realize you're not stealthing anymore. Lowering the height of the character more should be enough, however.