I understand how you feel. But take a step back and look at it from someone else's perspective. Divorce yourself from the situation; imagine it being a different issue and a different person.

Suppose it's a guy who suffers from migraines and is a firm believer in this natural remedy that will cure migraines permanently. Suppose that use of this remedy has given him an ulcer. Does it really matter that he strongly believes the ulcer is the result of having taken the remedy without food but now that he knows better he understands that it must be taken with food? Does it matter that he strongly believes in the theory behind the functioning of this remedy and that he firmly believes it will cure him in the long term? Do any of those things mitigate the fact he is a guy still suffering from migraines who is promoting the product that gave him ulcers and has failed to cure his migraines?

I still believe it to be morally wrong for the guy above to peddle his natural remedy given the fact it has given him ulcers and hasn't cured his migraines; the fact he believes he has it figured out now and it will work eventually is irrelevant.

I still believe it is morally wrong for you to promote a positive view of marriage when your marriage has been dysfunctional and has caused you seemingly irreparable mental damage; the fact you believe you have figured it out now and it will work eventually is irrelevant.

Yes, tell your story. But in my opinion, promoting Mill's views is morally wrong of you until your life can serve as an example of the benefits of having acted on such a principle. As of right now, your testimony would serve better as an example of why Mills is wrong than as an example of why he is right. You're the worst possible spokesperson for that view. So, why promote it?