Engineering help with prototype part made from 7075 Aluminium

Hello everyone,

I needed to ask some questions regarding a prototype that i have designed, the prototype part is a scope ring which mounts onto a mil spec 1913 picatinny system it has a recoil lug and has a clamp at the bottom which then is tightened by fasteners it also has a top clamp that is secured with fasteners around the optic.

My question is regarding the tapping of 7075 aluminium and the torque limit in my design I am using m4x7 grade 8 fasteners which i would like to have reach between 15-20 in/lb of torque on the top of the part and 35/50 lb on the bottom clamp i would like to know if this is achievable with grade 8 fasteners on a 7075 aluminium body i am planning to give life time warranty on the part and i am concerned about thread stripping etc.

The second question is regarding the thickness between the holes created and outer wall what is the minimum distance in mm that i can have a tapped hole near a edge or a wall of the part before it loses it's sructural integrity etc.

Please find the attached pictures of the design and it would make better sense of my questions.

I thank you for your help and looking forward on solving this with your help.