Dating men in your 40s and 50s is not only complicated by the so-called baggage they bring from previous relationships, but can also be complicated by a Disney land fatherhood situation when the man's kids are still young, or an over-the-top enmeshment with their adult children when the man's kids are grown. Either situation is completely dysfunctional, and very detrimental to the possibility of having a healthy and fulfilling romantic relationship.
It used to be a common complaint of men that their female partners were neglecting them because they were hyper-focused on their children, leaving no room for the man in the relationship. Women however, are starting to find that men can be just as emotionally unavailable due to an obsession with their children. The woman feels excluded from the man's life, because all of the man's emotional intimacy needs are already met by his (adult) children.
If the man you are dating is also a narcissist, you need to know that he is unlikely to let go of the control he has over his adult children. That means that their failure to launch as an adult is a calculated plan on his part to keep them close, and in fact the narcissist will continue to infantilize them.
Though you've discussed the need for self-sufficiency of adult children and the narcissist seems to mirror your values on that, he continues to be evasive about specific plans or a dedicated time frame for his adult children to start living on their own.
While your children successfully move out and room together as working students, the narcissist will sabotage all individualization on the part of his children. He will deliberately keep them dependent on him by not encouraging them to get a job away from home. There will be absolutely no plan at all for them to progress to independence as an adult. They will be permanently kept at a 12 year old level. For example, you may find these adult children calling other adults around them "uncle" and "aunt", even when they themselves are already way into their twenties.
The narcissist even has his sons frozen in time at that age in the only picture in his wallet, where you'd expect a picture of you to be.
Boundaries do not exist between the narcissist and the son he's married to. There will be 3 AM telephone calls by the son for mundane chit chats relating to a cute girl he might have met. When you are out on a date with your man, he will always take his son's calls, even though you've asked the narcissistic man to respect your together time with him.
It's hard to tell who is dependent on whom however, since the son will tell you: "My dad can't live without me." If through some miracle you get the dad to move in with you, the son may say to his narcissist father: "you've replaced me with her." Of course you will hear the narcissist boast about that since they love to triangulate you with just about anyone, including their own son. You are supposed to be grateful that the narcissist chose living with you over living with his son.
But wait, you will find that the narcissist is still intent on visiting his son every single day for more than 6 hours a day, after he moves in with you. You also find that they call each other 5-10 times a day. It all becomes more clear to you when you find out about the book "When he's married to his Mom" by Kenneth Adams. It's about an emotional unavailability due to enmeshment with a son. The adult child functions as a surrogate partner. The narcissistic man will financially support his son like he would a wife or girlfriend. They are a unit onto themselves. Frequently this happens in situations where the son helps out the father in the family business, and the father thinks he needs his son to secure his retirement.
It's really a delusional proposition however, and more likely just an excuse for the unhealthy enmeshment. The son only works part time in the family business and is praised for the minutest of accomplishments like running a credit card. The combination of his father's emotional hunger for him and a disinterest in teaching him real life skills is a recipe for breeding narcissism in his son too. Lisa Firestone calls this giving your son a buildup but no substance. The son is not at all encouraged to get a second job so he can strike out on his own. Keeping the son financially dependent on the narcissist is all about power and control. He is intentionally kept immature and incapable, yet at the same time the son enjoys being a kept man to his dad.
Truthfully, it also means there is no room in the narcissist's life for any woman since the position of "life-partner" is already taken with the emotionally incestuous relationship he has with his son.
You realize you were just a prop in the narcissist's life to bolster a facade of normalcy. At most you functioned as a welcome distraction from the tumultuous problems the narcissist was facing. Problems that were largely of the narcissist's own making. There was that problem with his other live-in son's criminal case involving the narcissist's own fire-arms, and a pending foreclosure on the narcissist's house to deal with. Though you had been super supportive of the narcissist's problems, your expectations that the relationship would improve once those problems were resolved were completely crushed.
Once your utilitarian function was fulfilled, it only became more abundantly clear that there was no room in the narcissist's life for you and you were relegated to the periphery of his life even more! His focus on "the son he was married to" only increased, and because of your own journey of recognizing emotional abuse, you had had enough of the mind games, the false promises, the pretenses and the lies.
For more information on the perils of dating men in your 40s and 50s, check out this informational video by Sam Vaknin, author of Malignant Self Love: Narcissism Revisited: Date from Hell: Dating Narcissists