Oh you need to get into that safe! Think Op, think. Does it just have a key? Or a combination too?
If he's always with the key you have two ways - force ie two big men to go to the house with you or stealth ie he is 'fast asleep' and you go in when he's there.
If there's a combination too then you need a cctv pointing around the combination so you can see it or two big men.
But if he's like 90% of people he leaves it unlocked a lot of the time so if you know when it's unlocked you can just walk in. A cctv in that room would do that for you. You can buy ones that look like nothing at all for £80.
You can tell I watch far too much crime drama but honestly what are you going to do? Let him take his daughters future away? Leave you a struggling single mum with no retirement? Destroy you financially as well as everything else?
Don't call the mortgage company without a plan. Otherwise they will tell him and you won't have access any more. You really need proper advice. Your solicitor sounds fucking useless. Are you in France? That's a real shame. You need to get in touch with the various DV charities and find an adviser, pref free, who can tell you how to play this.
And you might have to act decisively. You have access to most things including the house. It's your mortgage too. They were your rings. It's YOUR MONEY. Get a plan and don't try and do everything by the book. Just don't do anything you know can be proved and is a serious crime.
I've been burgled 3 times. Have the police looked for the burglars? No. The last ones wore gloves. It's your home and you are entitled to enter it and retrieve marital assets.
Stop being frightened and get a partner in this. A big, strong partner, even if you hire a bouncer by the hour.