You need to see a solicitor, and ask for a 'interim maintenance' before the final court order, this is calculate by you and your son's normal household expense how much he used to pay for the family.
As you said he earns high salary, does he get his wages through autopay into his bank account? Do you have any copy of his bank statement? Do you know where does he work? Keep hold all these info and pass to your solicitor. He/ she should know how to fight the best interest for you and your son. You know, if he refuse to pay in the future after the court order, you can go back to the court ask to attach his salary from his employer.
Don't be afraid, you are not alone and we all here to support you.