Good call. Because he isn't stupid. He knows he is in a funk. So your offer to help will go through his internal filters and be translated as, "You are a failure, and even I can see this, so you need my help."
And he is not where he can hear your help for what it is: A genuine expression of love and support. He will hear it as an attack.
I know from experience.
This is what ended my first marriage.