3rd I have no idea what your talking about MM wise. Reptile and a few others do tunes.
4th Why not just stick on a gen5 SC like I plan on and get a cam? For a DD no reason to have 2 cars unless ones broke. You can DD a gen5 SC car with a big cam so long as its done right and dont take any shortcuts. Chances are your getting real close to the limit of these transmissions too.