1./2. I haven't tried setting up my 990 in 6.1, so I'm not sure what the solution for you is there. I'd suggest giving Outlaw a call.

3. There are two ways to adjust the trims. One is in the menu (channel calibration) - that's how I adjust mine. Another is the TEST button on the remote, which I remember struggling with when I used it once. I had to check the manual (page 35) to figure out what I was overlooking. If you press TEST on the remote and then press SET on the remote a couple times, it will let you adjust the front left speaker. The up and down buttons will adjust the trim, and the left and right buttons will change the speaker being adjusted.