The Mod 3X3 latches extend past the main body of the charging handle by approximately 1.14" and the Mod 4x4 latches extend past the main body of the charging handle by approximately .91". Both will be compatible.
No, it is for AR15. Here is a link to a compatible DPMS GII ambidextrous charging handle:
https://www.opticsplanet.com/radian-weapons-raptor-ambidextrous-charging-handle-for-dpms-gen-ii.html
Yes, this should be compatible with the Savage MSR-15.
It will not. This is meant specifically for a mil-spec direct impingement AR upper receiver.
Yes, it will fit.