There is a very specific process for pursuing an appeal, and I don't believe that comes down to you just making an appointment "with Social Security." This is why I think it's a really good idea to be represented by a law firm. You mention a "paralegal," so maybe you have been involved with legal representation. Having the new medical evidence that you describe is just the sort of basis on which attorneys construct their argument that a decision against granting SSDI should be reviewed and overturned. There are deadines for submitting a request for an appeal. There is specific paperwork to fill out and submit. Attorneys know precisely how to comply with these requirements and how to collect the best evidence that needs to be presented and how to present it. For the sake of $6000, or so, I would team up with a law firm that specializes in disability claims. They can even possibly get benefits granted retroactively. Fumbling around with a process that they don't thoroughly understand, claimants have been known to damage their own case. Your husband has a lot of money at stake here. I would invest that six grand. Doing so might pay for itself, in the long run.

What you think "should be obvious" may not clinch the argument in your favor. The question isn't just over whether or not your husband can drive a truck. It's a question of whether or not he can do any work that allows him to be "gainfully employed," such as something he's never done before that he could be trained for. The way that argument can be made, or successfully refuted, involves thinking skills that go way beyond what is "obvious" to non-lawyers. The SSA doesn't really care about the diagnosis, per se. They care about "how does that diagnosis interfere with a person holding a job." Larry Flint (of Hustler magazine) earned loads of money even after becoming paralyzed from the waist down. People tend to think that they can present some compelling evidence, like the MRI you describe, and that the SSA will put two and two together and come to a reasonable conclusion. But the SSA isn't going to put nothin together. Not even some real obvious stuff. Making the linkages in a cogent presentation is the job of the claimant. Non-attorneys lack the training to know how to do that.

I don't think you're naive in believing your husband has a good case, much improved by new evidence. I suspect he has an excellent case if it's properly presented. I believe you may be naive in thinking that you and he can do that on your own. You may even be very smart people, but you lack experience navigating the system. The unfortunate reality is that who does or doesn't get approved for SSDI is not based on who most deserves to be approved. I got approved and, TBH, I've seen people more deserving that me get denied. I had a law firm helping me, and I spent a lot of time reading books and watching video presentations put together by lawyers. Go to YouTube and search "applying for SSDI."