So, you had a child by a married man who then disappeared as soon as you fell pregnant. So far, so predictable.
But then 8 years later you looked him up, and you messaged him to tell him he had a son, and now you’re refusing him contact? I understand that he’s being flaky as you say, but you were the one who wanted contact between them. If he goes to court he can easily say that you looked him up and are now refusing contact. It’s highly likely that a court would order contact, and then visitation, parental responsibility based on the DNA, and ultimately a level of contact.
And in truth you are the one who has kicked all of this off.
When you contacted him, surely you realised that doing so might mean he could e.g. eventually get eOW contact?
And no, at 8 the child’s wishes won’t be taken into account, A, because he never knew who his father was, and B, because it could be seen as parental alienation if he says he wants nothing to do with the man.
you have been incredibly naive here. No, he may not take you to court, but equally he might, especially if his wife is aware and wants to promote a relationship between him and his siblings.
And his siblings who are presumably older than him will one day know who and where he is and may wish to make contact independently when they’re all of an age to do that.
You need to see a solicitor IMO.