Your priority is for you and your children to be safe OP. You are not safe. Domestic Abuse happens slowly over time and you make incremental adjustments. Domestic Abusers often isolate survivors and they don't have anyone to reflect their situation back to them. They just have a gaslighting abuser telling them that it's their fault and if they do A,B and C then they wouldn't be abused.
It's really interesting to watch a woman describe her abusive homelife thinking it's 'not that bad' and for her to see the reaction of others. She's often astonished that others consider it that bad as she has been slowly adjusting to it for years. Women's Aid may have been the first time you've heard someone else react to your situation and you are minimising it and saying it's 'not that bad.'
I would begin by investigating an Occupation Order in order to remove him from the house. An Occupation Order can be obtained for free from the NCDV. An Occupation Order regulates the family home and power of arrest can be attached. It's usually granted for 6-12 months. The NCDV will assess your case and tell you if they can help, if they can, they will guide you through the process. If they can't, they should give you advise on what to do next.
Gingerbread have a specialised helpline and they can help you on benefits, child maintenance, child contact etc
You want to build evidence, so log all incidents of abuse. Print off any evidence such as emails.
Debt advice can be sought at the National Debtline. They can help you to pay off debts, give you advice on your options such as a debt relief order and advise on your credit score.
Read the CABx guide to ending a relationship. Laws vary depending on where you are in the UK, so make sure you read up on your area.
See if there is any counselling available from your local domestic abuse organisation. You can find your local organisation here. Give them a call and get support and advice.
Contact your local DV service at the council. Go to the council website and look up domestic abuse. They usually have all services linked. They sometimes have small funds available or others things such as the Sanctuary Scheme which secures your home.
I would also contact 101, have a chat with the police about his behaviour. Tell them about the spitting. Spitting is classed as battery under the Criminal Justice Act 1988 and can carry a prison sentence. Other behaviour would be classed as emotional abuse. They will also advise you on your legal options and how to gain evidence of domestic abuse for legal aid.
Be aware that his behaviour is escalating and, you are most vulnerable when leaving the relationship and the first year afterwards. Go about gathering information quietly and as unobtrusively as you can. Pack bags for you and the children should you need to flee and organise a safety plan to minimise risk.