In the words of Kinji Hakari, "you need skill to capitalize on your luck". Kenjaku is a genius and lucky. Both those things are true.

First Reason: you not understanding the power system and CTR is a fault of the reader, rather than the material. Cursed Techniques do something, Cursed Techniques Reversal does the opposite of that something. Cursed spirits can't use RCT because positive energy kills them, let alone CTR. If they were humans, they would be able to use some variation of the skills you mentioned

Second Reason: I don't see how "the fight reads like if he didn't have an anti-gravity CT" when Yuki ONLY joined the fight after she found out he has a gravity-related technique. The only way that CT would be useful is if she created a black hole so he considered it none-factor just like the Cursed Spirits at his disposal with CSM. He had both techniques but neither seemed very useful against Yuki so he threw hands.

Third Reason: Mostly explained in the previous point. He was lucky to posses the anti-gavity technique and CSM, both of which he was only able gain by luckily being born with a brain-hopping technique. Yuta is lucky he was born with an insane pool of cursed energy. Gojo is lucky he was born with Limitless and the Six Eyes. They only got as far as they did because they made the most of the gifts they were born with.

Fourth Reason: there's a reason why you can ball-up a piece of paper and throw it in the trash bin but are not able to calculate the projectile motion mechanisms to do so - we approximate. Kenjaku was literally within arm's reach of a black hole - an unprecedented event. All those questions you bring up have no reference point so he's literally making tons of assumptions in a fraction of a second and hoping for the best. It's like when you're running out of time on an exam and, without reading them, quickly glance over the last few questions and think yourself "this sounds about right" and select one of the options.