TM, welcome. My thoughts: 1. Don't be concerned with being close to the side wall; use the M22s outside the screen. 2. Get the M2 center, which matches the M22s well and should fit below the screen with room to spare. The foot or so difference in tweeter level wouldn't be critical. 3. As indicated, none of the speakers need to be behind the screen. 4. At least for seating near the back wall little or no toe-in would be helpful, and the question is apparently moot if you're definitely going to use in/on walls. 5. Probably not; the seating at the back wall won't benefit at all. 6. If you do want heights, QS4s with their very wide dispersion would be better rather than in/on walls. You might experiment with some small speakers that you have, temporarily positioned, to see if you care for the effects.
If that sub is a good one, the M22s should be fine. Note that the M22s use two mid-range drivers, and if anything, can play slightly louder there than the M60s with only one. Enclosure size doesn't bring any necessary advantage above the bass.
