1. Certainly. With three speakers, two of them are going to be getting the same signal (a left and two rights, for example), but you can easily configure the 990's second zone to feed a stereo signal to the extra two channels of a seven-channel amp and use those two channels to drive those three speakers. In this configuration, you could listen to a separate source in the exercise room (such as radio or a CD) from the active source in the main room (such as DVD or cable/satellite TV).

2. The 990's second zone also has a video output (composite or s-video) can can be controlled independently of the main zone, so this can be done pretty easily. If you wanted HD video, you'd probably end up pushing the same signal to both spaces and using a component video splitter/booster to do it, but if an s-video connection suffices (as would be the case for a simple LCD display like the one a co-worker just bought for his kitchen) then you could push a completely independent video feed to the exercise room.

3. I'd match the amp with the speakers being used more than the room size. Efficient speakers would be fine with the 7075, but less efficient speakers could benefit from the extra power offered by the 7125. Axiom could give you some good input on this (as could Outlaw, of course, but I know that Axiom is familiar with Outlaw's amps and has a very solid feel for how much power their speakers need and like to have). As for the sub, the Plus will allow you the option of achieving lower frequencies (a tuning point of 18Hz) than the standard LFM-1 (a tuning point of 25Hz, also available with the Plus when you leave both ports unplugged). Personally, my LFM-1 goes plenty deep for me, but if you really like to have the ability to hit the "so low you can't even hear that low anymore" notes, the LFM-1 Plus will give you peace of mind in knowing you can get there with gusto.