Sometimes my boyfriend does something I consider messed up (like breaking promises, cancelling plans, putting things off, etc). I end up getting upset and get mad at him. We end up having an argument/discussion. He gets really annoyed whenever this happens. Now he has even started to pull away, he even admitted he is starting to like me less because we always argue over "stupid pointless things". He is basically acting like I'm a nagging complaining girlfriend who expects way too much and gets mad over every little thing.
But I don't know what to do. I feel like he acts like a jerk/does messed up things and then he says I'm wrong for complaining! I am hurt by his mistake and I end up being the bad person, and get blamed for starting arguments.

You should break up. You are different people. He likes you less. You don't like how he acts, which is the same thing - he's not going to change! And neither are you, I'm sure. There is no right or wrong in most of what breaks up relationships.

But it seems like the main disagreement here is about whether what he is doing is REALLY a big deal or not. If he genuinely thinks its not a big deal and I'm taking it too seriously, then I don't blame him for how he is acting. If I was dating someone who was constantly complaining over every little thing, I would be annoyed too.

Just because he says your wrong and shifts the blame to you doesn't mean he is correct. Usually it takes two to make or break things in a relationship, but if he takes no blame, that can't be good. Why do I get the feeling things are going down hill? Oh because the lack of resolving issues is pretty much nonexistent. On of you is tired of the other, and wants out, so it won't be long before this is over with. Maybe that's for the best.

How long do you keep pursuing a relationship with a "bad match" after BOTH of you have started acting like it's a bad match and started trying to use the differences as a weapon to control/manipulate each other?

Dating is supposed to be fun, interesting, adventuresome, emotional (ugh), but most of all informative.

When the information you need finally appears (such as "I can now see what a long-term relationship with this person is going to be like"...), when the information finally is placed on the table, it's interesting what you do with it.

Put it away and keep "fretting", or start calling things what they are and start looking for your next adventure. It may be THE ONE, and you're not getting to it because of all this... whatever it is.

Again, you are looking for us to tell you who is right and who is wrong, and given that neither of you is a drug addict or criminal or abusive to the other, then what can we say? What you need is couples counseling. Somehow I doubt that he would go...
He has, as many people do, shown a side of himself that he may not have shown when the romance was young. He cancels, postpones, and breaks promises. You nag. He thinks you are petty, you think he is something of a deadbeat (not sure of the word you have in mind).
If we said you are 'right' (which I'm not going to do, not hearing his side), what good would that do? You'd show it to him and he would jump up and say 'I'm going to change?'
If we said you are 'wrong,' would you grit your teeth and force yourself to allow what you don't like about him to continue?
Don't hang on to love that has lost all the daily basics to getting through a day.

Disrespect, no accountability, blaming, distancing.

Before we get into it, answer me this: do you smother him? Men need space and time alone and with friends. If you're not allowing this, his destructive actions, are actually reactions, ones which are destroying your relationship. Give him space, encourage him to hang out with friends, and NEVER complain. He will appreciate his time with you more and sing your praises to his friends. Win, win.

If you're not smothering him, then he just flat out likes you less. Harsh, but this sort of thing happens. Relationships will always have an alpha and a beta, but the difference must be small, and there needs to be respect. Give him space, don't make any plans and see how he reacts, if he slowly disappears, it's for the best. If not, you will gain confidence in the relationship and he will gain confidence in you.

"If you love someone, set them free. If they come back they're yours; if they don't they never were."