I agree with using a disability attorney. They work on a contingency fee, which means that they only get paid if they win and they get paid out of any back pay benefits you are owed from SSA. No money out of your pocket.

It's nice that you have the help of your brother and his gf. They sound like they are very supportive.

As for your son's disability review, if you are denied again, in addition to looking into a lawyer, I would also write to your senator. When I was trying to get my SSDI for the first time, I was denied and ended up having to wait for an ALJ hearing. I was told it would be delayed for months and months. I wrote to my senator and had a hearing in two weeks. Worth a shot.