He will have to have the kids though, which will free you up to get a job
No he doesn't. Many many men completely walk away from their children and their responsibilities to them without a glance back.
It would be wise for you to get proof of the assets and his income but be prepared to get very little help and support off him if any op.
That said you ARE being financially abused (and as ever with abuse I fear it is unlikely to be JUST financial abuse that is occurring) and freedom from abuse is worth more than any amount of money.
Based on experience with a particular branch of my family I fear you may be married to an actual con man and you're one of his marks - it happens unfortunately
You're not married?! I have been flamed so many times for saying if you're going part time or gonna be a Sahm at least be married and yet here is an op who is incredibly vulnerable by being an unmarried Sahm.
Op I'm so sorry you have zero claim on any of his assets or income besides what cm you MAY be able to access IF you do some good research and get good proof of his income.
If it were a low income he could not have bought a £10k caravan just like that!
You need good, solid advice from a welfare rights and separation advisor.
You need to be VERY careful what you say to him.
PLEASE speak to women's aid before making any major decisions or alerting him to the fact you're aware he's taking you for a mug
DO NOT underestimate how vulnerable you are, if he senses or even knows (from you telling him) that you are becoming aware and he is losing control that could potentially lead to you being vulnerable to physical abuse.
Your and dc safety is the most important thing of all you must play this very very carefully please