Keep quiet and let him go.
For now, spend the next few days quietly preparing to get your ducks are in a row. If at all possible, see a solicitor ASAP, preferably before his 'trip'. As the main breadwinner you're going to want to know exactly where you stand.
Once he's on his way to 'his parents', if you have joint finances, move 1/2 the balance of all accounts to an account in your sole name. Find and hide (or move to another location like a friends) all important documents, birth/marriage certs, mortgage/rental contracts, all financial documents (bank, investments), copies of tax returns. If possible and you think needful, move any sentimental items and pictures of yours out of the house.
In fact, if he's going to be gone on a weekday, I'd either arrange the day off or call in sick. You'd have the house to yourself to get this all done in one fell swoop. Once done, send him AND his parents copies of the messages and simply say "We're done. Don't come home. We can make arrangements for you to get your belongings".
I know it's technically not 'legal' in a joint home, but I'd probably have the locks changed. Better to ask for forgiveness (and have to change them back) than permission.
Above all else, seek emotional support. Find a reliable and discreet friend or relative, tell him all and lean on them when you need to.