Bortleby,
I am so sorry that you are going through this difficult phase.
Some of the things you mentioned are so similar to my story... I was married for 10 years, together for 12 and then suddenly I was told by my husband he did not want to be with me nor pursue counselling.
I also made the mistake of pushing away all of my circle because I was so comfortable with him and wanted to make him a priority. So his friends became my friends, his plans became my plans. One good thing that came out of this though, was that, today those friends that were "his" and I made mine, stood by me like a rock through this time. Don't hesitate to reach out to your mutual friends (even though they did not start out as "your" friends)
My ex also showed absolutely no emotion, not a single tear when we were going through this... while I was walking around with red, swollen eyes after hours and hours of crying. So I know how it feels when your heart is literally breaking over someone while they just seem zen about all of it. But remind yourself that that is not your shortcoming. Maybe they just do not have the emotional quotient that you do. And that is not your fault in any way.

I got some great advices from people on my previous posts, specially to focus on yourself. Somebody suggested signing up for various activities on Meetup. I must admit I have taken my time to act on all of those advices but I have finally signed up for a session coming Sunday. I would definitely recommend doing something like that... or just to start with an activity that you thoroughly enjoy doing. And don't beat yourself up if you cannot bring yourself to do it rightaway. Allow yourself time to process all your emotions, accept them before you can make an effort to move on. But just keep reminding yourself that that is the first step you are working towards.

In the end, remind yourself that your partner is your past (I know it is a lot easier said than done). And you cannot work on your future until you let go of the past. You owe it to yourself, nobody else.

Take care and if you ever need a listening ear, don't hesitate to contact me. I am sure we can help each other through our experiences, which are similar in so many ways.

Love & hugs
Sushi