A "mental ward" sounds like the right place for your husband to sort out his problems, including his problem of not being honest about his daily life.

I think for both of your sake, you should tell your husband the way it is:

You cannot continue to carry the whole burden forever; he needs to be honest with all medical personnel or you will be; you're not going to continue in this crisis mode anymore; and the two of you are to come to some firm steps to take or you are going to start planning a life without him (because the reality is that divorce or death is inevitable if he continues the way he is.

How was he before you married? What has changed and why? It's worth it to put the time into figuring that out.

If he cannot maintain paid employment that doesn't mean he has to be almost 500 lbs; and he should be caring for the home if you are out working.