We are a group of five who rotates DMing with each quest. We have one DM who only does what he wants when he's DM, with no regard for other players, other DMs, or the rules, which forces the next DM in the rotation to scramble to salvage what is left from his quest. This one DM's quests consistently leave the PCs a mess in terms of advancement, items, and forced changes. We're trying to figure out what to do about this situation.
That's the short version.
The long version
Ok, so, a little backstory, and sorry for the length of the rant, it's kind of an urgent problem.
Me and 4 of my friends have recently started playing DND 4e, and it's been very fun. Only one of us, let's call him Tom, has actually played before, but it was the 3.5 system, and even though we picked him to be our DM, he was very bad, so we all decided to be DMs, each making a quest of their own, and then we would rotate, and it worked well at first.
Problem is, there's this one guy, let's call him Tim, who, while being a relatively ok DM, and while having a semi-interesting story, also gave horribly OP items (there was one where you take HP off of yourself, and then blast it around in a 5 square, and one that grants you resistance to all damage) and OP monsters (we're lvl2, the monster had 150HP, 1d10+5 dmg, but somehow AC 13? and there were only two of us against it), which are not balanced with anything, not with our level, nor are their stats balanced between themselves.
Tim spends a lot of time playing video games, and believes that DnD is just like one, that you can quickly lvl up just by killing enough goons and using enough coins, and then buying things that are useful. He thinks items are useless if they don't deal 10 dmg, which goes against all rules, and refuses to actually read Adventurer's vault or Mordenkainen’s to see whether there is an item with the same powers. When his quest was finished, he refused to take the items off, and half of them were either "soulbind" or were actually a skill that some ancient order taught us. The problem is obviously that now John and I have to completely re-devise our quests to accommodate his OP solutions.
As for monsters, he of course wants us to fight a god or an epic hero every week, because it is, of course, not fun at all if the monster is normal, even though he knows I almost killed the whole group using just 5 wolves. He then justifies his OP items by saying that it is our reward for killing the OP monster of the week, without realizing that the OP monster itself is the problem! When my friend and I, let's call us Jack and John, told him there are no solo monsters on lvl 2, and that we just jumped a level (in two sessions), and would jump another even if John does absolutely nothing in his campaign, he just told us that then we should lower the xp amount we get from the solos.
He thinks the story isn't interesting if there's no dying, and no gods, and is constantly devising new ways to be "stronger than anyone else". We don't know whether he's to lazy, or just not capable of actually devising a story that makes sense, without resorting to crude methods of raising the tension such as character death, and does not see a problem in that. His newest quest, he hints, will involve traps that might kill us immediately, and while that is totally ok, his quest seems to consist only of said traps and, of course, op monsters. He also always comes up with ways to block our abilities, or take them away because it suits him (for example he makes a monster that is completely magic proof, rendering our wizard useless, or just limiting our choices in a way that's not game-compliant), but of course throws a hissy fit if John or I try to remove an out-of-this-world item.
He even made a God of evil, stronger, of course, than any other God in existence, and then had him like us (?!) and give us gifts, which turned us neutral evil, even though we tried to explain to him that we don't want to be evil, that it doesn't matter that we're neutral, and that there's no way for an item that's not legendary to affect us that way.
Tim also seems to hate the rules (everyone hates the rules, but they're there for a reason), and has started inventing his own. For example he invented a "dodge" system, which no one understands, not even him, and which would only be used by him, and only some times, and sometimes not. His system is so arbitrary that not even he knows what he's doing, and where he has used it and where not, leading to constant arguing.
Tim justifies his new "better" rules by saying he's "bending" them. Well, John and I, being the nerds we are, pulled out our ye old Player's handbook, and DM guide, and read them cover to cover, and nowhere did it state that creating a whole new game constitutes bending. It has come to the point of us allowing him some small changes, so we can limit him on the big ones, but the small changes are somehow more annoying, as is his constant whining about something not being logical or realistic (because we're not playing a game where a character gets run through by a sword, and gets 5HP dmg)
We, of course, tried talking to him, and explaining that he has to think things through, that he can't just undo his mistakes by doing something even more questionable (he now has 2 persons in one body, a dragonborn paladin, and a genasi something, which he is able to change every day or so), and that we are not comfortable playing something so unconnected with DnD. He completely ignored us, or worse, didn't get the point at all, playing stupid, and making us debate him on some small things until we come to the point where we contradict our first intent, because what he has planed is much worse. Tom, also, seems to want to follow in his footsteps.
Our question is this: How do you deal with such a DM, as a player and a fellow DM? Is there a way to keep him down, because if we throw him out, then Tom and Angelo also go with him, and while we will do it, it's kind of our last option. Can you give us some arguments to support our wanting a single DM (to which Tim will most certainly not agree)?
We have googled it using every phrasing we can think of (and John is a literal Google Guru), but most of the solutions given seem to be: "Talk to him, make sure he understands, he will be reasonable". Problem is, he isn't reasonable, and with us being 2:2 (Angelo doesn't count since he doesn't care), it's kind of starting to be more trouble than it's worth.
The dilemma about starting a new game with just one DM is featured on reddit so if you have any arguments supporting just one DM, it would be much obliged!