@ash16,
You've long ago gotten your closure. Life has gone on and for the better (at least for you). This man is hurting now and quite selfishly behaving.
Let it rest. No need for a reply. In fact, a reply should be avoided at all cost. There'd be a difference if the relationship hadn't ended badly - but it did end badly and you suffered due to it.
Continue enjoying your new life and your husband. Impulses should sometimes be set aside. Your husband appreciates you and this would unsettle him and you know it. He doesn't deserve to have the seeds of doubt placed in his mind.
You have got a best friend (in fact, quite a few) already. If this man was truly thinking of you as his friend, he'd have left you alone.
P.S. FWIW, I've also got an ex with whom I'm in touch regularly but we were never married. We never lost touch after our break-up; however, we met at age 50 and broke up 7 yrs latter with no bitterness.