It’s very sad. It would be weird if it wasn’t sad. It’s ok to remember good times fondly.

You could clean and declutter the house, pick his stuff up, box it but don’t get rid of it. Talk to him about what he wants to do with it. Give him time frame. If it’s not removed by then, it could be pitched.

Contact legal aid. Or a lawyer. Document the day he said he is moving permanently. Make it official that he left. It could start separation period. Keep everything in writing. Texts and emails. Save it for documentation purposes in case he later says he just went on vacation or something