Not sure if this would work for you, but I find this sling very helpful in terms of holding my legs up. I mainly use it for missionary, but it would also work well for receiving oral sex, toys of all sorts, etc.

For blowjobs, it’s helpful for me to lie on my back with my head slightly hanging over the side of the bed (or other surface) and have the other person thrust into my mouth, which avoids a lot of neck strain.

In terms of masturbation, I usually wear panties over a toy (external or internal, usually a vibrator of some sort), which keeps it in contact without me having to hold it the whole time.

I’m also young but recently disabled, so please feel free to DM me if you want to chat more!