I worked as caregiver, husband in another country, no income, not PR. What should I declare on his T4?

If he didn't receive a T4 slip, then you shouldn't enter any T4 slip info on his return.

Also, if he's not a Canadian resident and has no Canadian income, then he might not need to file a tax return at all. This FAQ has information about determining residency status: https://turbotax.community.intuit.ca/community/tax-filing/help/how-do-i-determine-my-residency-status/00/873440