That's correct. You should just write your answers with M, G and R instead to avoid confusion. And the break up velocity is reached with an "=" sign, not ">" or "<".
You're basic force equation for a masse "m" would be:
F = -mg +N = -m(v^2)/r, but since the normal force N equals to 0 you get...
Normally the distance between the center of the spheres is considered much greater than the radius so the charge movement within the spheres is neglected.
Considering the initial charges q1 and q2, and the respective charges q3 and q4 after the spheres were connected. You've found that q1q2 =...