I don't have experience with needing to let go of an ex-T like this, but I have had similar experiences with exes and at least one very close friend. I think your T is right, that it's over. But I think you shouldn't try to put a lot of pressure on yourself to feel better in a particular timeline. Feeling a lot of distress and running through thoughts about your T in a loop are basically a guaranteed way to stay stuck and wanting to reconnect, even when your logical mind knows that isn't possible.

One thing that I've found helpful is to focus on making my life better, and as time goes by, it starts to feel like I'm in a completely different place than I was when I was when that person was such a big part of my life. When my life has changed, it feels a little like the space that person occupied isn't so empty anymore. You mention some things going on in your life earlier in the thread, but they sounded mostly like stressors and worries. I would recommend finding things that make you happy but are productive and somewhat energy-/time-consuming. Only you can know what this is, but it might be exercise, a new hobby or craft, joining a group, taking a class (online or in person), working on a creative project, volunteering, etc. Things like that can be both a distraction and a way to help you move forward so you aren't feeling so stuck.