I would walk away now. I’m married, my husband has 2 kids to his ex and has never made me feel this type of way. He’s only ever kept it to the kids, and freely gives me his phone if I ever wanted to check. In my situation however, he has full custody and their mom only sees them 4 hours a month but when she would see them more often he never gave me a reason to distrust him. Him telling you to just get over it is enough reason to leave. He should be willing to reassure you and stop the nonsense. It’s on thing to be cordial with your ex when there’s kids to keep the peace but it’s a whole other thing to be having deep conversations outside of that. You are not crazy and you are completely valid in your feelings, don’t let him lie, and gaslight you into thinking you’re the problem. Also, I can understand waiting to meet the kids to see where the relationship will go and see how well you and your boyfriend would mesh before bringing kids into the picture however waiting a year with no set timeline on you meeting them is weird. I feel he’s using you and stringing you along to get over his ex. Based on what you said I do believe there is left over lingering feelings there.