I have been receiving advise on here that says I should seek out advise through the courts though.
Most of our members report having possessive ex's. (My ex is possessive to an extreme, there was no way for us to avoid family court.) So since they know they'll end up in family court sooner rather than later - or are already in court - they are encouraged to take a
proactive rather than
defensive posture. (As they say regarding football, a team never won with only defensive plays.) However, in your case you have an ex inclined to stay in the background so it may be smart to handle it as you've been doing since a mere mention of possible testing, past DV or legal encounters might keep him in line and not causing problems.
But 18 years of parenting is a long time and your situation can change. For example, be aware that if you ever go on government assistance, the agencies may require you to disclose your child's other parent's name so that person can be garnished to share the support expenses.
If you suspect he might expunge his prior record, then I'd suggest you go down to the court and get copies to hold just in case. If it gets expunged then maybe you can't use them in court, but you can still wave the papers around for good visual effect. You can never have too much documentation.