Remove the money in your isa in cash. You'll need to do this in regular chunks over the next few weeks.
Get a fire safe safety deposit box and securely store this in the roof space at your mums house.
Leave a small amount in the account, a few hundred pounds.
Then say nothing about this account. And more importantly do not instigate divorce proceedings for about 9 months - 1 year from the time of withdrawing the money.
You only have to submit the last 12 months bank/ money transactions when a court asks. If a solicitor asks you can ignore, it's only a court judge who can insist. Anything prior to a year at that point this is disregarded.
Play this cleverly. Because it's a sure thing he'll come after you for half that money. But at that point its him who can take you to court and you who can show that the money isn't in the account.
Remember the year rule. Deposit that cash asap.
As PP have said as they marriage was brief you may walk away with all your assets.
Keep proof you paid for the dogs. This is important. Make sure they are registered to you and I'd change the registered address to your mums house.
This helps secure your rights to them .