It's an invented prescriptionist rule that was imported from studying Latin. You can completely ignore it and you'll get more natural sounding language.

Same here. There's probably other ways too, but personally I'd probably have gone with "and we're okay with that" or "and that's fine/okay with us". Just flows more like naturally IMO.

BTW, in spite of the tongue in cheek way in which I said it, I meant no personal ill will towards you. Just the rule and its tyranny 😉

It's the "with which we are okay" that sounds a little stilted. Most speakers would probably phrase that part of the sentence as "which we're okay with." It's just because "okay with" is so common that it almost feels like a transitive form of the verb "to be okay," so splitting apart sounds odd.

Note that there's already a different transitive verb "okay" which means "approve" or "authorize," as in "the boss okayed your plan to use the forklift," implying that the person doing this has authority or control over whether the thing happens. "I'm okay with it" by contrast typically means something like "I have no control over it but it also doesn't trouble me." "Unfazed by" (spelled in this way, not related to "phase") would be a similar expression.

What you wrote was fine. Some people don't like that sentence structure for stupid reasons