1. the HOLES can easily fit 7 inchers, the stock BAFFLES/SPACERS im not sure. mine allowed 6/6.5 while other eg baffles were only 5 inchers, not sure why.

best to take your grill off and have a look. take out the baffles if you need to, its only 4 screws. there will be a measurement somewhere on the plastic spacer, look for that.

thats said i would just get new mdf spacers made, the stock baffles are 'leaky' as hell.

2. wouldnt recommend doing that. if you feel like your gonna be 'wasting' channels then use the amp to run the fronts 'actively', but that might give you more headaches...