The blender will work fine, but you should either let the bread sit out for a while (or just use stale bread to begin with) or toast it a little bit. Then I would put small amounts of bread in there at a time and pulse until it's fine bread-crumb texture.
The problem with this is, most of the salt comes from the bread itself. You could just buy plain, unseasoned dry bread crumbs and get the same amount of sodium.
An alternative is oatmeal ground fine in the blender. If the crumbs don't blend evenly, turn off the blender, take the container off and shake it up, then blend again. You could mix this half and half with the bread crumbs so the salt is cut in half.
I've been on a low sodium regimen for years now, and I'll tell you, it was the hardes adjustment I ever made. You have to read every single lable and watch for hidden sodium.
Just grate your prefered slices of bread with a cheese grater.
Use whatever kind of bread your husband can tolerate, and toast it first! Then use the blender until it is to the right consistency. Toasting it first works better than letting it get stale, and makes it much easier to work with.
What you eat can have a direct effect on your skin if you're struggling with psoriasis. See what to shop for.