They all make sense. The best one is: I’ve never wanted a couple to work out as much as I have with you.

They are mostly interchangeable. In my experience, recall is more often used in formal settings. Remember is almost always used in everyday conversations. Recall has a second definition, which is to take something back after it was given, usually due to a problem. (I.e. The car was recalled when they found out the airbag was defective)

It means “things get worse.” It’s an expression used to say that things didn’t go as planned or things turned out bad.

Also, the word you should use is “importance”, not “impotence”. Impotence has a very different meaning...

Yes, they mean the same thing. The second one sounds better and would more commonly be used.

"If you say so, who am I to disagree?" The way you wrote it works too, but it definitely needs a comma and this way sounds better.