I went through the EXACT same things with my father and it was very frustrating. I tried to stay calm and not let it get to me but sometimes it did. Do you know what that taught me? That getting upset with him to where I could tell him how unfair and hurtful he was being was the only way to get him to see how awful his behavior was. I always felt guilty afterwards but he became more patient with me over time. It is a horrible thing that our loved ones are going through and it is horrible for us as well. We want to be there for them in every way possible and in their frustrating sometimes they push us away. It's not personal, they are losing their independence, their pride, their way of life and their lives... but it is hard not to take it personal.
As my fathers illness progressed he became less mean and once he stopped fighting against using a wheelchair and accepted it, he became more receptive to help for the other things he needed help with. When he moved to Hospice he allowed his friends and family to visit more frequently and has mellowed and seems to appreciate them now. It has been a tough battle to get to this point where he is actually content... but he's there and I hope that your husband can get there sooner rather than later.
I didn't read everyone's comments but I'm sure that someone must have suggested that maybe your husband can come on here and talk to some of the others that have ALS. It could help him to know others understand EXACTLY what he is experiencing. However, if he is anything like my Dad, he won't want to surround himself with others like him... his solice has mainly been in getting drunk each night (I now put the Irish Creme straight into the g-tube) and watching animal planet. Acceptance comes in waves and your husbands youth, as well as him having a young child, probably make this all the harder for him to accept. He doesn't want help, he resents needing it, he hates what is happening and maybe he thinks that by refusing what he needs that he can deny the illness. Unfortunately the mental part of ALS is brutal for some and while we want to be perfectly patient, it may not be the healthiest choice. Talking to him bluntly when he is NOT in the middle of a tantrum may be an option... that's the best thing I can suggest. It helped when I did that, when Dad was rational enough to listen and feel some shame for his behavior. Maybe it would help with your husband?
Take care of yourself, get the help that YOU need and lean on us here... we understand and we care deeply.
Sandy