You are doing wonderfully. I know that was horrible to deal with, but you did everything right. Good on you not letting him in, and good on you ringing the police. I know how difficult it is, how frightening it is, how guilty you feel, how confusing that is... I know it's a total nightmare, but you've got this.
Have you filed an official report with the police yet? If you haven't yet, then when they finally do turn up, please tell them everything you've told us. It's definitely not too late, and they will let you choose whether or not to press any charges. You need his behaviour to be on file, though, so that if he keeps this up there will be a solid record, and they'll know they can't take their sweet time getting round again. Allow them to take photos of that nasty slice up your arm (it looks awful love I'm so sorry!), any bruises you have, and any items he may have broken as well. Tell them what happened the first night, AND what happened when you called them to come over. They will let you decide what to do next, and they will have information and advice for you.
You never know what he could do, or to whom, and he may get even angrier and more dangerous now he knows you're serious about splitting. Even if he has no reason to, he may well turn up again, and the fact he didn't turn tail immediately when the police were coming tells me he's not terribly bothered about them. You must protect yourself.
If he turns back up, ring 999 rather than 101. They already know about him now you've rang them, so they may be more understanding next time and hopefully quicker. And don't speak to him at all. Don't even tell him to go away, don't tell him he can come later, don't tell him ANYTHING. Keep the doors locked, and ring the police to come round immediately. If you think of it, try to record him if he's out there shouting or banging on the door or windows.
Also, don't answer if he rings, and don't reply to any texts or emails. Keep a log of his contacts - at least do not delete any of them - so that if he starts harassing you that way, you will have all the evidence, and the police can act on it. If he starts to contact your family or friends, make sure that they do not delete his contacts, and make sure they let you know about it.
It may be a good idea for your parents to record their interaction with him, when he goes round theirs to pick up his things, as well. He could act out, threaten them, tell them plans he has to contact you... who knows. If it's not too late, you may want to tell them to do that.
Hopefully none of this will be necessary! He may well take the hint and go away for good and all. He very well may get his things and never contact you again, and I genuinely pray that's what happens. But I wanted to get it all down just in case, because you never know about a man who could hurt a woman. You just never know. :(
Keep strong. You really are doing wonderfully! And remember, we are here for you if ever you need us. Loads of us have been through this ourselves. There is nothing you can't say, nothing you can't ask. This is your thread to vent or say or ask whatever you need to!
(sorry this is so long! i hope some of it is helpful!)