How do you occupy a Husband.

He can go in the garden and potter.
Remind him,if he lifts anything,he could end up back in hospital.look through the window ,or sit out there with him, take a book, or crochet, just in case he forgets.
It's not for long, be patient.good luck.deep breaths.

Play scrabble together?

giulia good suggestion!

Lego or an Airfix kit?

Could he plant some seeds, prick out seedlings, a bit of pruning etc?

Try going onto JIGIDI free jigsaw puzzles online. All levels and all subjects. A lot of exchanges among members too, for example: if he's interested in gardening he could try the plant section.