Is 75%in general and 65% in sc/st is the overall % required in 12 to give the jee mains as well as advance.

Overall 75% for general and obc students and 65% for sc and st students is required to get admission into NITs, IIITs, and other CFTIs.... And this is also the minimum percentage required to become eligible to give jee advanced after clearing the cutoff in jee mains.
But you can attend jee mains even without this minimum percentage ...there is no eligibility criteria decided by cbse in concern to minimum percentage for attending jee mains. Hope I could help.

75% minimum is required in PCM not overall.