Michael,
Before I answer your questions I want to point out that, in real world situations, the "best" speaker placement isn't always possible. Physical restrictions caused by room size and layout, furniture placement, etc. often dictate where things are placed.
Don't agonize over it. Do the best you can, then sit back (or, as in your case, lie back), relax and enjoy the movies/music.
Generally, it is recommended that the distance from your ears to either front speaker should be the same as the distance between the speakers; speakers 8 feet apart, your ears 8 feet from each front speaker. Having said that, sometimes I'm the correct distance from my M60s, sometimes I'm at my desk farther away. I think things sound good in both situations.
The 60s have two rear firing ports and they need room to breathe. It has been said, that they can be as close to the back wall as 3 or 4 inches . I suspect it is better for them to be a little farther from the wall, but I wouldn't worry about it.
Depending on how close the M60s are to the A/V center, the front surface of the speakers should be, at least, an inch or two farther from the back wall than the front surface of the A/V center (out in front of the A/V center). You don't want sound reflecting off the sides of the A/V center.
The ideal positioning of the 2 front speakers and the center channel speaker is a subtle arc, with your ears roughly the same distance from each speaker. Again, I can't achieve that exactly with my setup. If you can't either, don't make yourself crazy about it.
