If that's what he wants and that's his opinion, that's fine. If she agrees to it and also wants that. Does he dress modestly for her as well?

He should also be consistent about it. If you believe that, then you believe it 100% and you act it out 100%.

None of this, it's okay when he posts the pics but it's not okay at an Usher concert.

You don't pick and choose modesty like that. You're either modest, or you're not.

Lastly, if that's his deal, why is this just coming up now? What is he doing partnering with an entertainer, knowing.that provocative dress is often part of the job and affects their livlihood? I don't see him refusing any of them money it provides out of this sudden sense of moral indignation?

You can agree with his opinion on modesty. Lot of people do. At least also admit that he's weaponized his opinion to attack his partner, behaved inappropriately, and is being a hypocrite about it.