There’s a couple of angles to consider here. First, Claire was never the sort to be controlled, and Frank was never the sort to be controlling. Sure, he demands loyalty, but what you do and how you do it in your service to him is your business.
Second, Frank really wants to see her happy, and he’s just not up to the task of providing her with sexual satisfaction. When you’re young this sort of thing is all-consuming, just the thought of your wife getting satisfied by someone else is like the worst thing in the world.
When you get old enough you’re just glad seeing someone get satisfied. My grandparents like to prod the grandkids on their relationships, and I can tell they get a certain thrill from it.
Frank’s sexuality has always been wrapped up in his thirst for power, and he has all of it he could ever really want. So there’s no latent frustration to work out sexually, like he did with Zoe or Meechum. His bond with Claire runs so much deeper than ‘mere’ sex could ever really honor. I haven’t watched the whole season yet, so I’m curious as to whether the show will find an appropriate liaison for Frank this time around.
I rather enjoyed the scene where they were standing out on a balcony and Claire was having some doubts, and Frank points out at the crowd gathered outside the White House to give her some perspective. Frank got satisfaction out of that, the act of dominating her mentally. She wanted more, and was willing to blow off her date with Tom to get it. Frank, true to character, sent her along to a less-satisfying rendez-vous. It’s his MO to leave others unsatisfied while he himself gets all he wants.