The OPs feelings and everyone else’s here are completely correct and valid. There are no right answers.

A few of us here are coping with estrangement from an adult child and it’s interesting to that issue as to what we are discussing here. A painful rift may be too personal to share at first. My own values would definitely force me to disclose something as important as a child I created to a prospective spouse when that relationship started getting that intimate, but I see other’s opinions vary. It would also want to know why he had no involvement/child support. These are important facts to have to form the decision whether this person is a good life partner for you; worthy of trust.

Also, aside from the disclosure issue, he has been emotionally invalidating, and the whole relationship was moving in a direction very quickly and not in the right order of things as most people do. But, those are personal choices, too. Not judging.