Getting Stuff Back and Unfinished Business

Just to give a little backstory: 6/7 month relationship. Was really good most of the time. But we bickered a lot (both strong personalities). Last few months were not great because I am moving to a new country soon and he doesn’t want to do LDR— this caused a lot of tension between us. The breakup was really messy (I didn’t handle it well because I was already in the middle of a personal crisis), but it was also not the first time either of us tried to end it. I don’t think we will get back together but we still have some unfinished business.

I have stuff at his place (a lot) and he has a few things at mine. I have some files he needs for a project and he has some I need for a project.

Also, we go to the same school and have numerous mutual friends. So there is a high chance of running into each other. And my birthday is coming up and I was planning on throwing a big party and inviting my friends (some of whom I met through him).

So my questions are 1) how do I handle getting my stuff back and asking for the files I need? And 2) what should I do about inviting mutual friends to my party (this might also be the last time I could see some of them before leaving). And lastly 3) what do I do about the high likelihood of running into each other?

Thank you in advance.