This is the experience that we had with a military disability. It has been so many years, but here it is. It takes awhile. You have to be dilligent. Check to see which benefits are better and which work for you. There is SS, SSI, and military disability. Each of them have levels of disability and different criteria. Some let you work, some don't. I would check all of them out first.
SS pays little. SSI pays more. Military gives you more leeway. Even if you are disabled, they allow you to take full time government jobs with a full disability it it doesn't hurt you.
This has been our experience.
As for the success for fusion, they have to tell you the worst odds. If you follow all of the rules and have a positive outlook and attitude, it can be done. Bone grows. The ones that it doesn't work for are those who think, hey, I don't really have to give up smoking, caffiene, sodas. I don't have to exercise and walk, walk, walk. You have to want it to work.
I have a brother who had full back fusion about, I don't know twenty, thiry, years ago and he is now working in FL, lifting garbage cans into trucks for a living. He back gives him trouble once in a while, but he takes Motrin for it.
There are a lot of good people on this site that you can turn to for support and answers, more than you can at a doctor's office,