Is he the sole earner? If so, you're not working either way. In that case, what is the point of FI, supposing that he wishes to keep working? Is your concern that he will lose enthusiasm for work later, leaving you both destitute unless you start to work? By asking him to put nose to grindstone, are you asking him to trade his present for your future security? Is your thought that his high earning time is limited and should be harvested, leading to his own greater happiness later on the assumption he won't want to work at that point?
I'm normally very pro-FI, just not sure I understand this case. Please forgive me if I accidentally offend by these questions. Congratulations in any case on saving, learning about FI, communicating with DH, and finding new work options that are exciting to him. I will defer to wiser commenters and any further remarks by you.