Yes. The Tasco 3-9x32 .22 Rifle Scope w/ Rings fits to 3/8 dovetail rails like the one found on the Marlin Gelnfield 75c. It will fit and function as intended.
This scope does include dovetail rings.
You will want 1" scope rings. Height will depend on the firearm the scope is being mounted to.
The Mossberg 640 uses a 3/8 dovetail, however, it is not long enough to fit a standard scope ring setup. You will need an off set set of base's as it has screw holes on the side of the rear of receiver. Or you can purchase BKL offset rings to replace the scope rings that are included with this optic, you can find the BKL offset rings using the following link:
https://www.opticsplanet.com/bkl-technologies-model-302-1in-long-double-strap-offset-dovetail-rings.html
Yes, this scope will handle recoil levels of most centerfire cartridges including the 6.5 Creedmoor.
Yes, the rings will work for your firearm. When measuring the dove tail rail, you want the outer diameter or the width of the rail.
It depends on the size of the dovetail groove of your rifle. The included rings are for 3/8" dovetail.