I experienced the same problem with one of the derby bolts. Use a dremel with a cutting disc, cut the bolt head across the top and down to the washer, relieving the torque pressure. Drilled with a 5/32 drill, used a snap-on spiral easy out and bingo...Steel machine bolts into a aluminum case; locktite or anti-seize use is fine. Torquing is key.

 

+1 locktite and min torque in the specs. Remember the only thing those bolts do is keep the gasket sealed, and the gasket only has to seal against splashing and not pressure. It ain't retaining any structural force. You could replace the cover with gasket goop and a piece of sheet plastic if you wanted and it would be fine.

+1 on the silicone o-ring being reusable forever as long as it isn't distorted.