Your husband did not get into a “gray area” because he lost his job. He did something illegal because he was unable to hold onto his ethics and was willing to take the risk. Since he persists in seeing his mother as a “saint,” it isn’t healthy for him to live with her as she will support him in denying responsibility. Not questioning his mother’s view of him as perfect is partly what got him into this fix. It may be a relief to him to have more contact with his mother with whom he doesn’t have to deal with the blame and shame that go with his actions, but it won’t be helpful to his personal growth.
The problem you both face now is not where he lives, but whether he is willing to grow up and man up. That means accepting responsibility for his actions. That means making it clear to his mother that (a) he did make a serious mistake and (b) that she must be respectful of the woman he married. If he can’t be an upstanding citizen and a loyal husband when in the orbit of his mother, then he should put some distance between them by looking for other jobs. But that only takes care of the immediate problem. The more pressing issue is whether you are married to a guy who is worthy of your respect.
I wish you well.