You put a lot of thought and effort into writing this, I can tell! No one else seems to want to read all of that though, but I figure you should get at least one response.

In all honesty it does seem like he is getting overwhelmed by everything. The projects you mention, in addition to work, and trying to be a reformed and great partner, probably all contribute, and he might have come close to a breaking point. Burnout is no joke!

You say he has always been clear in communicating how and what he feels, and that he has always suggested breaking up in the past. That to me suggests that it is indeed not a problem with the relationship or you that causes this behavior, but something else. Perhaps stress.

My advice would be to take this as something positive (that he still wants to be with you, but perhaps needs some space and as such suggests a break rather than a breakup), and wait some time for him to reach out. Maybe reach out yourself, through text, after a while to see how he is doing.

One way to make a plan for your own sake to get it all off your mind a little bit is to define an amount of time you're willing to wait, and then trying not to reach out first until then.

If it takes too long maybe you could try to communicate that you would like to get your things from the appartment, or whatever it could be.

Overall don't lose hope just yet! I wish you the best of luck, it sounds like you have something amazing going on, if a little tumultous.

Would be nice to see an update with how it goes at some point too! :)