Trying to taper down off of methadone is no picnic. You are *going* to crave and have thoughts of using while you're going through the process. Don't feel bad, it happens to everyone.
One thing I would like to suggest is this: Stop tapering down for a while. Accept the situation that you're in, you have to work at the moment, etc. Rather than worrying about getting off the stuff right now, why not just work your @ss off, save up some money, and then try to get yourself into a position where you can take a month off of work and go check in somewhere? Yeah, it'll suck kicking methadone in rehab, but I'll tell ya what ... you gotta a LOT better chance of pulling it off there. And when it's done, you're gonna have a very valuable experience under your belt.
Personally I think that approach makes a lot more sense than trying to taper down and eventually (ostensibly) quit methadone while you're going on about your life and working and all that. Because 'all that' ... is damn near impossible to pull off. All you're gonna end up doing is getting yourself fired, and/or back on dope eventually. Get real, and don't try to be superman. That's my best advice.