Mad Catz R.A.T. 3 mouse problems on MacBook Pro
Download the R.A.T.E software from madcatz (under software), that allows you to wire up keys to forward and back, as well as setting the DPI properly.

Note, you have to allow the app in Security &amp; Privacy after install completes 

The inverted scrolling wheel is due to OSX treating all mouse as a Magic mouse. Changing the scroll direction to natural in system setting will affect both the touchpad and mouse, which is annoying because the touchpad direction is right.
I recommend Scroll Reverser which applies scroll direction separately.