Most Helpful Guy
Day by day. And, by realizing you were not at fault. He initially misrepresented himself, intentionally or unintentionally, by stating he is over the breakup with his ex. And, by consistently reinforcing that by spending an usual amount of time with you, given the short time you knew each other, and introducing you to his family and social circle. Thus, you eventually trusted in him. It could happen to anyone.
By the way, the statement, "there were issues with his son and his ex," in my opinion, means he and his ex are not entirely over each other and, or perhaps are contemplating reuniting. Parents who are no longer together but still have feelings for each other will often take issue with their children being introduced to their co-parent's significant other. But, who knows, there could be many reasons behind his decision.
That being said, going forward, consider it a red flag when someone wants to move things along quickly with you. I believe, at least, they are fleeing from something or someone, or they are very much insecure or dependent. Relationships should progress at a natural pace.
For now, occupy your time in new and other interests.
Most Helpful Girl
I was a rebound before and it hurt so much... this guy has drama and you should not involve yourself in his mess. Find someone who has no kids. Good day!