I'm sorry that your husband is in pain, Shawnlee.
Subluxated shoulders, if that is what you mean, can be helped by reconstituting the joint while doing exercises such as bending the arm at the elbow to keep the other parts of the arm flexible. Essentially, this is holding and guiding the shoulder back toward the spine, which doesn't erase the subluxation but minimizes it as much as possible.
A PT (your doctor can write an order for one to come to your home if your husband finds it difficult to get out) can show you; make sure you get one who knows about ALS and subluxation. Always padding the elbow and forearm so they are not put under pressure, and of course, never doing anything with the arms that pulls the shoulder the other way, is good as well. You have to watch everyone from aides to lab techs, as there seems to be a habit of pulling patients' arms forward.
I also recommend a low voltage heated mattress pad at night, and range of motion exercises (always holding the shoulder, elbow, wrist, knee, ankle, that is being moved, with one hand) and gentle massage in the morning especially. Again, a PT can help design a routine that you can perform. With this kind of shoulder problem, he likely cannot be rolled, or only if the shoulders are supported. As his legs/core are affected, you may want to have a slip sheet under his fitted sheet to pivot him in the morning, if you have help, or we can suggest other options if it's just you.
If this is the flail arm variant of ALS (the one most likely to cause subluxated shoulders), it is a slower-moving version of ALS (average survival said to be ~5 years) and it is very unlikely that any other joints will dislocate as long as they do not suffer undue stress.
Apart from the shoulders, this form of ALS generally goes through the various issues like arms, legs, core, breathing, eating, swallowing, talking, etc. but some people who have it are less likely to have problems with eating and talking, and breathing until later in the disease, or less severe overall, and that is why survival is longer on the whole than with more common types of ALS.
Best,
Laurie