the vortex razor HD gen3 is a 34mm tube this mount is a 30mm mount it will not work.
ATN does not state the mounting space dimensions of the ATN Thor LT. The Midwest Industries High QD Scope Mount might work but I recommend contacting ATN to confirm.
Offset refers to the location of the rings in relation to the base. A 0 offset means the ring are right above the base. A 1.5" offset means the rings are moved 1.5" forward from their normal position. This is usefully mainly on AR-pattern rifles.
Any of the 30mm diameter models of the Midwest Industries High QD Scope Mounts should work fine with the Swampfox Arrowhead 1-10x24.
To determine the correct Midwest Industries High QD Scope Mount you need will depend on the specific scope model and rifle model you are using. The guide at the link below will help with determine what height Midwest Industries High QD Scope Mount you need.
https://www.opticsplanet.com/howto/how-to-how-to-measure-scope-height-scope-ring-height.html
The Burris Eliminator III has an integrated mounting system that mounts the scope to a picatinny rail base. The Midwest Industries High QD Scope Mount will not work with that scope.
The Midwest Industries High QD Scope Mount mounts to picatinny rail. It will mount to the picatinny rail on the receiver of an M&P15.
The Midwest Industries High QD Scope Mount, if properly installed, should have no issues with the recoil impulse found on the FN Scar.
Yes, the Midwest Industries High QD Scope Mount will work with that scope and rifle. You will need one of the 30mm diameter models of the Midwest Industries High QD Scope Mount for that scope.
The Midwest Industries High QD Scope Mount model MI-QD30HDSM has a centerline height of 1.5".