Yep, up_threshold at 75 should help a bit, at least in some usecases.

Safety... is hard with CPU overclocking.

I'm not an expert, but I'd say, for the time being, unless you're getting spontaneous reboots, you should be okay. Long long term, you might get unlucky and your CPU may wear down because of the overclock - but that's entirely a matter of luck - your CPU may be fine right now and forever at those frequencies, or it may be fine now but develop some fault a year from now. *Shrug* I honestly have no clue.