1) Yes the VTLs will drive both sets of speakers. The main issue with Magnepans is clean power with good current. Magnepan's are a steady 4 ohm load so aren't that hard to drive just need strong current.
2) 1.6s are not really harder to drive than the 1.2s, they will just go lower and will play louder if given more power.
3) Recommendation is tweeters on the outside edge. Your room is plenty big to take advantage of the Magnepan's qualities. I suggest 4 from feet out from back wall and 7-8 feet apart. I sit about 9 1/2 feet from my speakers but your room is bigger so you have more options. The speakers are very easy to move so experimenting will provide you with the best sound.
2) 1.6s are not really harder to drive than the 1.2s, they will just go lower and will play louder if given more power.
3) Recommendation is tweeters on the outside edge. Your room is plenty big to take advantage of the Magnepan's qualities. I suggest 4 from feet out from back wall and 7-8 feet apart. I sit about 9 1/2 feet from my speakers but your room is bigger so you have more options. The speakers are very easy to move so experimenting will provide you with the best sound.