OP you really need to speak to a solicitor dealing with family law ASAP. Most offer a free advise / consultation session.

Try and see one this week as they are mega busy after Christmas!

You can get a court ruling which covers you for child support and access. As a VERY rough guide for one child it is about 15% of your take home pay.
You should be able to have equal access to your child.

If your wife gets very nasty call the police.
It will be best if you are whiter than white.
Keep a diary of everything that happens and is said.
Maybe worth you phoning your sons school / care provider and explaining the situation to them.

You also need to think about any joint debts you may have.

I hope everything works out for you and your son.