I'm so sorry that you lost not only your friend, but access to so many memories.
I just want to understand a bit here cuz it's not super clear -
Your girlfriend went onto your Facebook account and unfriended and blocked him, but that's it? Didn't delete your account or delete individual media or anything like that?
If so, it's very possible that you could contact his family for help. They may be able to download his user data and send it to you (or just the pics and stuff) so you have a permenant copy. idk if they are planning to memorialize his page, but if they do, you could also request to be re-added (and if they don't plan to, perhaps request to maintain his memorial page yourself).
You can also download all of your user data, some deleted stuff makes it through if it was deleted more recently and the archive hasn't purged. This also goes for messages, iirc. Google images may also have some copies of photos on their servers from trawls.
Take care of yourself, and regardless how the data aspect goes, maybe consider grief counceling if you can and aren't yet. It can make a huge difference when you lose someone so significant to you, particularly when there are other interpersonal issues tied so tightly to the situation.