Your divorce will have to go through court to be finalised, but they are unlikely to finalise unless you both have a share in the equity in the house - he would have to try to convince a judge that he doesn't want any equity.
But the comment also adds up to racked with guilt...again pointing to a third party being involved. This happens just when you get back from holiday - a holiday that means they have been apart and are desperate to be together - thus it's helped make up his mind to leave. To you it's out of the blue so he hasn't even mentioned being unhappy before - that's a very big leap.
I'm sorry but to make a general sweeping statement a man will often sit in a marriage until something or someone makes him want to leave. Men are creatures that will stay somewhere, even if they think the relationship is over.
How does this effect you op, it will effect you as someone else is pulling his strings and so all the advice here about playing your cards close to your chest are worth while keeping at the forefront of your mind.
Your loyalty is to your DC, not their father.
I would do a few things, on your own.
Get your house valued
Contact district council and tell them by email you are living along and give them your oh forwarding address and your bank details to collect the council tax.
See if you can get an hour for free with a solicitor to get some advise about your situation
Get a summary of your mortgage, a list of your out goings and income and take this type of information with you.