@jheieck I'm so sorry you are in this situation. It's clear that you are doing your homework and trying to find a reasonable solution to what is unfortunately an unreasonable problem.
I'm going to ask some questions, offer some speculations, perhaps some possibilities and one paper on discontinuing Prolia.

First do you really have to make the decision to stop Prolia right now with no time left as your 6 months period is up?
Maybe take one more Prolia shot and give yourself another 6 months to think this thru.

Is the Feb knee replacement driving this in one direction or other?

My opinion is do not stop Prolia without some drug transition. Too dangerous. Evista or bio-identical hormones could help somewhat but not at all likely to be enough.

If you could see one of the top osteo doctors you could get some advice on how to navigate this. And of course you need expert dental advice also. There should be doctors and dentists who have already dealt with this situation. Perhaps a consult with Keith McCormick could be helpful.

Perhaps staying on Prolia is your best choice or does that make your dental situation impossible to live with?
Is one or two infusions of Reclast definitely out? I know your jaw bone problems are not a good starting point for using Reclast but you are weighing all sorts of imperfect options here. I'd suggest not ruling out anything based on general rules.

In weighing the decision whether to stop Prolia I can offer some slight clarification of the consequences.
There are two slightly different huge factors to consider when stopping Prolia esp after long term use.
I make the distinction between the two because the odds of them happening and the consequences if they do are related but quite different.

One, without a follow up most everyone will lose the gains they made with Prolia and sometimes more that what they had gained. Depending on where you were when you started that can be pretty awful but it does not mean you will have the multiple spinal fracture problem. Maybe you will lose a lot of bone but not start fracturing.
Number two is the multiple fracture problem. As far as I know no one knows the frequency of this problem. We know it happens but we don't know how often. We know it is more likely if you've been taking Prolia longer but I've not seen anyone suggest a way to predict who this will happen to.

So, almost everyone stopping Prolia without a follow up (and one that is successful) will lose their Prolia gains. But it is unknown what percentage will have the multiple fracture disaster. I guess that it is a fairly small percentage of those stopping Prolia but that is just a guess and no comfort to those who suffer this
consequence.

A wild speculation on my part is that you could try to transition off of Prolia with Reclast and if successful then do a bone builder (Evenity, Forteo or Tymlos) to restore a more healthy bone building/bone remodeling climate. This is just theoretical but in looking at how to deal with osteoporosis long term we need to find out if we can alternate between antiresorptives and bone builders. Perhaps shorter courses of each after the first early rounds of them could lead to a healthier balance between building, remodeling and resorption and dodge the ONJ and femoral fractures and bones that are too brittle?

Sorry this was so long. I wish you good luck with your decisions.
Here's the discontinuing Prolia paper:
https://e-enm.org/journal/view.php?