This answer is probably not going to be any better than any other answer, but I have to point it out because you're new to role playing and I feel it's important to see the whole picture. Everyone else is giving good advice, but it helps to have some background on why they're giving that advice.
The DM's NUMBER ONE Job is to Make Sure Everyone Has Fun
That means that everything else, including the game itself, is secondary.
This DM obviously doesn't understand this concept. You are (and he knows this, trust me) obviously his best player. You take the most interest in his game, you spent the most time on character creation. You are the block of gold in that group. If what he's doing is making the game less fun for you, he needs to stop doing it. Period.
I've Been in Your Shoes Here
I have been in every different type of group. There are groups where you can't do anything that's not explicitly listed in the rules. In these the fun is lost because of limitations that are presented by situations the rules couldn't possibly account for. In your position, the DM has taken the other extreme. Throwing out the rules altogether can make for interesting story, but it also leads to misplaced expectations. This is a case where you can expect abilities to work differently every time you use them.
At that point, why bother having character sheets at all? Freeform RPGs are very popular, but 4e is not one of them. Tell your DM to pick a different system if he doesn't like 4e's rules. Or better yet, tell him that if he doesn't like the rules in the book, then he's writing his own book, and believe me, that is no easy task. Every new DM thinks he can write his own brand new system for role play. The time spent on well-balanced, accurate, fun to play classes is not something to shrug at. It's no wonder WoTC still struggles with it every release of D&D.
There's a Reason There are Rules
Rules, in any game, whether it be D&D or Soccer, are a way of making the game fair, balanced, and entertaining for everyone. There will always be people who try to read too much into the rules in order to beat the system. This is what a real rules lawyer is, after all. The concept of rules in the first place though is so that you have expectations. So that you don't encounter a creature covered in spikes and say "I want to charge him" only to find out that, in this situation, charging will somehow impale you on a spike. "I didn't want to grapple him" you might say, but the rules changed this time, and charge = tackle today because the DM thought it was funny. That's not fair to anyone, especially you.
You're Not Innocent Here
This part is the hardest on people, especially new players, but all I've heard here is your side of the story, and how you tried everything to be what this guy wanted. There's always another side of the story, so remember that when you go into this group. While all of us are giving you advice on how to talk to this DM, when it comes down to it, he spent hours, maybe days working hard to prepare his game for your entertainment. So when you sit down at that table, whether you agree with him or not, his way goes. This is part of the reason almost everyone here is suggesting you leave the group rather than try any other tactics.
I didn't say the DM was right in how he does things, but you're at his table playing his game. If you don't like it, and he won't change it, go somewhere else. This is one of the things I love about my current DM. He calls it your game and he is very amicable to changing the way he runs games based on the players in his group. Still, his games will always be in a mature setting with extremely challenging decisions and that's how he chooses to run.
There are Other Players at the Table
The second part of this is the other players in his group go there for his DM-ing style, as it is. So when you're asking him to change, you're affecting other people. I wouldn't want someone to tell my DM to run silly dungeon crawl style games because that's not what I enjoy. I like the challenge of out-thinking a bad-guy who is just as smart as I am. I would not enjoy a game where I kill all of the monsters in a room and open a door to more monsters with no real goal or purpose in sight. So it's important that you consider the other player's opinions.
The DM is Human
I feel like a broken record on this, but everyone, and I mean everyone, tends to forget that people in a position of power are just as human as everyone else. Your DM is going to make mistakes, and I'm not just referring to rules mistakes, but he's going to have personality flaws. He may have had an issue with an actual rules lawyer in the past, and found that the only way he could respond to rules arguments that would end them was "stop being a rules lawyer". He may have gotten annoyed with the complexity of 4e rules over time and just given up trying to learn them.
More importantly, he may have spent so much time on his storyline that he's now nervous that if he starts using the rules more strictly, that one bad guy might not live long enough to tell you guys some vital piece of information, or that one good guy might get killed in the fight where you were supposed to join in and defend him in order to move the story forward. This could be a defense of his story, which he has definitely worked hard on. Be careful that you see things from his perspective and remember that it's not easy to keep a whole bunch of people working toward a common goal.
That's all I've got to say.
I'm not going to attempt to tell you what decision to make partially because everyone else already has done that, and partially because I'm not there. I don't know if the joy you got out of the game is worth the sacrifice of the joy you get from using the right ability to counter the enemy just right (that is a good feeling too, and I enjoy it from time to time). I don't know if you have a lot of options for other Role Playing groups in your area or if you're somewhere in North Dakota with no one around for hours of drive time. I won't pretend to be in your shoes, and so I can only tell you what I know, from experience and study, of which I've done a lot. Good luck with this decision. It's a tough place to be, especially when you're new to D&D.
