Life is always dealing us blows of one kind or another. Children are a challenge even when they are model citizens. You have to keep in mind that the two of you together may be better equipped to deal with his problems then if you were at each others' throats. That is not saying that you must stay together to present a untied front. Also keep in mind that if you can't talk it out between the two of you then perhaps outside help is needed and that is true whether it is a vanilla or a BDSM relationship.

One other thought is your son will eventually leave the nest and if you are allowing him to split you up now you may live to regret it later. Just a thought.

Good luck.