I actually agree with this for the most part.
Look...I'm not going to say the dude isn't at fault here, because he is. He said he was going to follow through with something at a certain time but didn't. That was wrong, and I personally have never done this as a seller and would never want to not ship something on the day that I said I would....unless something just came up that was unavoidable. But, I honestly think you overreacted BIG TIME....and because of this, you are in the bind that you are in.
You would have been better off just letting him ship it a couple of days later and then putting him on your "DO NOT DEAL WITH" list for future transactions. Instead, you blew up on him....threatening to demand your money back....then actually demanding your money back with a "right now or else!" attitude and then wonder why he has not gave you a refund yet. Sure, he could have gave you a prompt refund, but now that you pissed him off severely, he obviously figures "how about I just fuck this guy around, sense he keeps threatening a paypal dispute...I think I'll let him just do that before I ultimately give him the refund." I'm not saying what he is doing is right. It's just the way the world works....you yank on someone's chain....odds are, they'll turn around and do the same if possible. You just took it to an entirely different level that it didn't need to be taken to.
And, this whole "I was expecting it to be here by the weekend without question!"....is totally irrational. Like the other dude said, you are dealing with an individual, not a business...you should not expect a tight deadline. There have been many times I purchased something where I expected it (in my mind) to arrive around a particular time, but actually did not show up for a slight bit longer. I just shrug it off and am glad I got it later, even if it took slightly longer than anticipated.....as long as were talking within a manageable time. I think, maybe something came up on his end that delayed the shipment....I just don't go ape-shit over a couple of days. Call me crazy?