Not that there is any way to excuse this crazy (sometimes scary, sometimes violent) behavior, but there is a sad truth to this: He is more miserable than you. He can't let go because it's likely that he lacks a sense of self-worth. As such, he feels he needs yours to survive and he will seemingly stop at nothing to get it.
Being that you are a nice person, you will try to get him to see the logic of why it didn't work out between the two of you. Or, his outrageous behavior (4-a.m. phone calls asking to see you) will have you wanting to take care of him through the breakup. Sorry, but that doesn't work. You cannot take care of someone though his/her own lack of growth.
What you do need is some distance, clear thinking and an honest evaluation without wishful thinking or denial on your part. Don't take his phone calls. Don't accept his deliveries. Stop participating. Don't have your friends or family intervene. And stop thinking it will correct itself. Visit your local court clerk and investigate getting a restraining order. A note about restraining orders: Even if you do get a restraining order, you are not necessarily safe. All it means is that your stalker is legally supposed to stay away from you — it doesn't mean that he will. A restraining order will make arrest and prosecution easier, but it won't necessarily stop him from stalking you — or worse. Use your best judgment about obtaining restraining orders. Depending on the circumstances of the stalking, you may be able to have your stalker arrested for trespassing, threatening communications or other crimes he commits.
In the meantime: No matter how crazy he acts, try to realize that what is happening isn't because of anything you did. Crazy behavior is just that. Unbalanced people do what they do, but that doesn't mean you caused anything. They are making choices — and that's not a reflection of anything you are, or have done or not done.