first, why did you take the fuel rails off to do plugs? don't do that ever again it's not needed.
when you striped these screws did they thread in really tight? or could you finger tighten them in but then you decided they need 7,000,000,000 foot pounds of tourqe to hold down that coil..
it a little tiny 7mm bolt threaded into a insert. you may end up buying a new intake if you can't fix the inserts. and judging by this I don't think you have the level of skill needed to do the job, I suggest a new intake or bring it to a pro.
sorry I am not trying to be a jerk, just being honest with you.