1) So with the volume set to 0dB, calibrating with the test tones forces you to crank everything down a great deal? It's a little unusual, but not necessarily a sign of anything wrong. Keep in mind that you are not restricted solely to the 75dB calibration point - if you wanted to, you could set the volume to -5dB and calibrate to 75dB (which would raise all of your trims about 5dB). The big goal is consistency.
2) In general I strongly recommend keeping the space above an amplifier unobstructed. The top of the 7100 is covered in vents for a reason - that's where the air passing across the heat sinks wants to go. If you don't have a separate shelf above the 7100 to set the 950 on, I would suggest adding an inch and a half or two inches of spacers (wood blocks roughly the same size as the 950's feet would suffice) between the two.
As for testing it out, I'd suggest grabbing a few of your favorite CD's and DVD's and giving them a spin, see what you think of the way they sound with all your new gear.