My ex-wife and I were divorced approx a year ago in Florida and we still live in Florida. Part of our agreement was that I would continue paying her car lease and then buy it out for her. Well, due to unforseen circumstances I am not going to be able to do that or a few other items in the MSA. What will happen if I do not abide by the MSA contract? I plan to continue paying alimony and child support.

She could take you back to court if you don't keep paying for this. If you can, file a motion for modification of this MSA as soon as possible before this gets out of hand.

Yes she can take you back to court and have the judge order you to pay,
With the "or else" if you are not going to be able to pay, I would contact your ex and see if you can work something out.