Unfortunately, that's not how World of Warcraft works. Once you get to a high level you do things called "dailies". You can do 25 per day, and it's a main source of in-game income (gold). You can only do them once per day, and they reset every day at 3:00 AM Server Time. You need to think of WoW as a Hobby, not as a "game". It's a hobby, and establishing that will make things easier. To keep things constant - especially since the newest patch for Crusaders is upcoming - you HAVE to do these dailies to earn Crusader's Seals, which are used as bind-on-character currency for special items and rewards. I do my dailies every day, however, I prioritize. I get them all done (it can take me 2-3 hours of on and off playing to max out my 25 dailies), and then I'm done with them. I play the AH and then I check around on things I may or may not have to do before (or after) going into the real world. Blizzard takes care to make sure WoW doesn't get boring to their customer base - it's how they make money and at the same time entertain the customers that aren't completely obsessed.

Armed with this knowledge, maybe you can give a shot at establishing new limitations for his hobby. Give him an amount of time to play every day, 2-3 hours for dailies (I feel 3 hours is a little long). You also need to figure out when he raids (raids can take FOREVER until they die enough to call it). It is RARE that a guild raids every night of the week. He's not allowed to raid every night a week, no, it's too time consuming an it makes people frustrated. Raiding is a full guild commitment, and if he doesn't do it he could lose his DKP or raid spot. UNLESS he's pugging it. P-U-G is short for Pick-Up-Groups. These groups are formed when random people just join together in a group to try it for the hell of it. Sometimes they do well, sometimes not. Be sure to figure out which one he's doing. Pugs can be sacrificed, guild runs are not so much. Ask him which is he's doing before saying, nope, if it's not a guild commitment or you're not in your alotted play time - no go. Do not let him say "oh but ...", that's not how it works. Until he stops playing so much and starts working on repairing the relationship he needs to prove he deserves to spend time with you. Imagine yourself as High Inquisitor Whitemane (she's a fairly sexy NPC boss in Scarlet Monastary), if he wants to get his hands on your loot he has to get through the meat shield of dedication (let's call it Mograine). He's pulled wife aggro! Tell him to use misdirect and to focus fire.

Besides daily times he's set for dailies, and weekly times that are set for raids, there's also Achievements, Wintergrasp, battlegrounds, and Arena to consider. To fix this, give him one or two days a week he can play as long as he wants (as you've been trying). Maintenance is from 5:00 AM server time to 11:00 AM server time on Tuesdays (if memory serves, I'm not on all the time so I don't keep track). This generally means that it's rush hour to get things done both right before and right after. This means, set a bedtime. The healthy players I know have bedtimes, or times when they "call it". They know when to walk away and to cool off, or when to take breaks. If your husband is the breadwinner and feels he "deserves" something to chill out on, he has time he can do that with. Spouses have been "chilling out" after a long work day by doing other things besides WoW for centuries. If he needs to get to a "safe place", make him hearthstone (takes you to your saved Inn location), or mount up and log out on a flying mount. It sounds like he's leveling an alternate character if he also raids - BEWARE THE ALTERNATE CHARACTER. It's exactly like you said, one more level! One more level! They're like potato chips. Once you're in the zone it is HARD to break out. On my alts I set visual goals, one-two levels, done. Maybe just half a level, or I set a goal to clear certain quest hubs. His alt is not as important as his main character - and for damn sure not as important as you - make sure he remembers that. Make sure he remembers what he had fun doing before that, and if you have to, set up dates for intimacy. Sure it's bare minimum, but it's better than nothing, and we're banking on the fact that he'll eventually start doing it off-schedule on his own.

If anything else, try the game yourself. It's fun, I swear, once you get past the general douchebaggery and just play for the hell of it. If people are asses, don't let it bother you, and ... don't tell them you're a girl right off the bat. It's fine to let people think you're a guy until you get to know them better. If you come swinging out of the gate screaming estrogen it really turns people off and makes people think you're either lying or you're ... an attention whore. No girl gamer wants to be that girl.

Regardless, I hope this helps. Getting involved with his hobby can show a lot of support, and it also means that you gave 110% to trying to help the relationship. You two could end up playing together, it could devolve into a simple fun time hobby instead of a massive time-consumer, or ... well, I don't want to say anything negative. Let's hope for the best.