As stated in the OP, I've already ran the math. About 5 pages back to back running the different conservation of energy/momentum/mass equations, and found all kinds of mathematical relations. The answer I was looking for was what Ken G gave (thanks BTW).
Right, you're basically just stating what Compton did in his original paper; the difference in wavelengths is equal to the Compton wavelength of the electron times 1-Cos(theta). So I guess if you want to deal with it in terms of wavelength, what is the significance of 2 times the Compton...
So when you calculate the scattered electron energy and the scattered photon energy (for 180 degree deflection) you get roughly the following (in keV).
Photon(in)__Photon(scattered)__Electron(recoil)
27.5_______24.8______________2.7
81_________62_______________19...