the best thing to do is to go and speak to his higher self and ask his higher self to guide him towards the right healing experiences he needs to be able to move on.
His higher self is always with him and knows him best; but they tend to also be a bit floaty and unless someone asks them directly to interfere, they don't.
A simple, heartfelt meditation with a single candle when it's quiet is all that's required to contact someone's higher self.
Just close your eyes, put your hand on your heart (you can hold a photo of the ex if that helps) and say to yourself, "I want to speak to (x)'s higher self. Take me there."
A representation of the higher self will appear (they usually look quite a bit different from the physical person you are familiar with) and you can talk to them.
Remember to ask specifically and DIRECTLY for what you want them to do.
Also remember to be respectful and to thank them for talking to you at the end.
One word of warning.
When you contact someone's higher self, it is customary to be totally blown away by how beautiful and shiny they are. If you don't watch out, you can fall back in love with the ex! It's normal to feel very drawn to someone's higher self - anyone's higher self, for that matter.
Should that be the case, contact your new boyfriend's higher self straight after, because that too will be shiny just the same and attractive to stabilise the current relationship and not get any weirdness happening.
Good luck with that and some additional star dust,