Yikes, he should have put that on the table in the first place. Read your comment about moving on, that is exactly what you wanna do. No need to be strung along with some wishy-washy “eventually”. Be with someone who wants what you want and wants only you since you’re looking for a monogamous relationship.
Time spent dating or in a young relationship is about learning if you are compatible with the other person and if they’d make a good life partner for you. The biggest mistake you can make is ignoring the signs that they aren’t the right person for you or thinking you can change them to make them the partner you long for.
He’s clearly told you he doesn’t want an exclusive/monogamous relationship right now. Since you’re not OK with that then it’s time to say goodbye and continue your search for Mr. Right.
Tell him that he is free to have an open relationship — with someone else. You already told him that you are not interested in being in one.
This is a tricky one because there are two likely scenarios here as far as I see:
(1) His true desire is to have an open relationship and he is bending to your will in order to not lose you. Not a good foundation and I think you made the right call ending it since the two of you seem to be fundamentally misaligned in this case.
(2) He is struggling with some fear of commitment because he is afraid to get hurt if he invests too much in one person emotionally. He used the open relationship argument as a cover-up to protect his feelings. That’s a vulnerable place to start a commitment from but hey, we all have baggage. Not a deal-breaker, in my opinion.
Really, HE needs to tell you which one it is and then you need to decide if you believe what he says and draw your conclusion accordingly. If you can, it might be worth talking it through face-to-face with him.
He wanted an open relationship because his last ex cheated on him? “It would be easier.”…
In short: he doesn’t trust you and expected you to cheat on him from the beginning. He has major trust issues and should not be in any relationship for a very long time.
Forget him and move on.