Given the fact that you admit your marriage is what led you down a path that has thus far culminated in seemingly irreparable harm to your psyche. Given that you also admit that it won't be clear whether you made the right choice until "the long term". I think it would be morally wrong for you to promote marriage. It would be akin to someone promoting a weight loss program that they are sure will work long term and that they are certain will work very well if people do it right, but that has thus far only led to irreparable muscle tissue damage when they've used it.

On the other hand, neither do I believe it would be morally right for you to promote a view you don't actually believe in. Thus speaking out against marriage is not an option either.

So, my suggestion would be, don't give any advice at all. Instead of advice, share your story. There is a lot to be learned from hearing your story; tell the story and leave it up to the person hearing it to decide for themselves.