Hello again and thanks for the extra info.
As you and your boy both live in the UK, and his dad hasn't seen him at all for about 4 years, I can absolutely reassure you that no court will take your child away from you.The dad would not only have to prove that you are a bad mother, but he would also have to prove that he could care properly for your boy AND that your son would be happy to live with him. It's not going to happen.
The law on child support is quite separate from the law on who a child lives with, and what contact the child has with the other parent. A dad could be great with his kid and get to see the kid lots - yet be penniless and not have to pay hardly anythign in child support - or a dad could be really horrible and the court order that he is not alloed to see his kid at all, yet be a millionnaire and have to pay megabucks in child suport.
Unfortunately, now that you have made an application for child support, you have reminded your son's father that is IS the father, so that might make him decide to apply to court for contact - ie to see your boy - but the decision of the court will not depend on whether or not he has paid any money in child support but on what is best for your particular child.
There is a possibility that the court might agree that he could see your son - but any contact that was ordered would only be in a way that was safe for both you and your son, and that you could both cope with eg it could be an hour a month at a contact centre. But if the dad missed sessions, or turned up late, or left early, or misbehaved in the contact session or was threatening to you, so that your son was upset as well, you could bring the case back to court to ask for the contact order to be revoked.
I think you would benefit from some face-to-face legal advice.Here's where to ifnd specialist family law solicitor:
I hope this helps and I wish you the best of luck.
Thanks and best wishes...