100k miles is about the limit. some people go longer but its not advised because eventually they start peeing fuel instead of atomizing it and they can burn a hole in your piston
have you ever thought about cryoing your block? that might stop it from cracking more. i would try to get a optimizer block, steel crank, main studs, cryoed and shot peened rods, roller rockers, balanced rotating assembly. fluidampr, delta cam, and slightly lowered comp ratio maybe 20:1 and...
i know what your saying. i had to cut off the tip of a screwdriver to turn the fittings so they were snug and i couldnt reach with a wrench. its hard cause there brass and they chip easily. but otherwise it was a great product and my fittings do not leak 1.5 years after i installed them