A lost spark situation, especially intermittent, is often hard to track down. Some of what you think may be causing it might be coincidence (only when hot...how do you know for sure it was not only when the wire was not jiggled by the opening of the hood?) or they may bear on the original root cause. Usually ignition components effected by heat are the coil, power stage (the two are integrated in this case) and maybe the CPS...particularly it wire.

I actually would suspect a bad plug more than a cracked boot on the wire IF it truly is heat related. You might find cracked or partially missing porcelain on a plug if you look close enough.