@henderson1005 You have so much going on. Snaps me back to Jengo. There's no easy or right or wrong answers. Just keep trying till you run out of chances.
When Jengo first came home he couldn't walk, so we were given a RuffWear dog harness with a handle that I could use to hold him up as we started the rehab. I wrapped a leash around the handle so I didn't have to be bent over as I walked him. He too had the knuckle under issue. Maybe not as bad as your guys does. Still, I'd consider a harness with a short short lead lashed to the handle.
I couldn't let him anywhere near stairs, so I gated them off completely. I'd carry him up and down. But, once it became clear that he needed to urinate much more frequently, he and I moved to the down stairs bedroom. He needed to go about every two hours. After weeks of this I was pretty sleep deprived and didn't trust myself on the stairs at 2 and 4am. Moving us downstairs helped a lot.
A few months after he'd been home his anxiety began to peak. I think it had much to do with switching from Phenobarbital to Potassium Bromide (KBr). Gabapentin and CBD helped, but was seemed to help more was getting on the floor with him and talking to him. Try putting him into his dog bed, lay him down, lay next to him and talk. I might hand feed him some snacks, but mostly... just talk. That seemed to calm Jengo more than anything else as I recall. I remember just laying there with him nose tip to nose tip looking into his eye and talking.
Much of the lower floor is all tile, so I bought dog play pens to keep him contained mostly to the carpeted areas. I didn't like seeing him slide out and smack his jaw on the tile. We also moved carpet runners to parts of the tile that he needed access to. For instance, from the family room to the back door. He also began to get tangled up in end tables and chairs, so those were stored elsewhere.
To me, it was like bringing a toddler into the house. I did everything to make it safe, but he was great at showing me all the things I'd missed. I just had to keep watching him.
As far as the aggression towards your 5yo. This one is frustrating. I will say that your little one watching you care for and modify your life to care for you dog will prove to be a life long lesson of love and compassion. I hope other members might chime in on this part. I don't know how to correct this, and I'd be asking for help too.
Having been through something similar... no judgement here... regardless your choice. Take care.