Of course, al of your examples are contractions. To my American ear they sound a little weird without two "haves." - If I could have, I would have done it already. Or, If I couldda, I wouldda done it already. That's how I wouldda said it.

I agree with the above but the title should read Are these ok?All are ok isnt really a question more a statement implying that they are correct without question.Hope this helps

The only problem is in your third example. It should say "him/her" not "his/her". Otherwise, all are okay.

Everything is correct except this: "If I could, I'd have divorced his/her a long time ago." In this sentence, "his" should be "him". Remember that "his" is possessive. "I like HIS shirt". So, the correct phrase would be: "If I could, I'd have divorced him/her a long time ago." Everything else is perfect! Good job!