I'm so sorry you deal in this. It's been a mess.
Sounds like X is off to seek new supply sources. And since it cannot be
him doing bad behaviors, it has to be like something is broken about
your personality for not enjoying it. I hope you don't take his text tantrum outburst personally. He sounds messed up and like he wanted last digs.
That whole thing with X saying that you mourning the loss of your grandfather was "unacceptable" that you should hurry up with it -- jeez! I suspect that was him wanting your undivided attention and mad he wasn't getting it. It just has to be "memememe" with him.
I hope things look up for you soon. I am sorry Y is hurting. That's not fun. I also hope you are able to comfort since you want to be there for him.
I also hope Y learned some things from the experience too -- like how to better handle his NRE so he isn't blind to serious caution flags. Some people just are not good dating partners. X sounded like a doozy.
Hang in there!
Galagirl