I feel for ya..sounds like it's pretty much
all day long when having to deal with Mumbles.
Sounds like it's time to sh*t, or get off the pot.
I had/have a similar situation, but it is with a "peer" that is a "tard", but the boss is a push-over (no balls). "Tard" makes trouble in the dept, only get's half the work done of everyone else, but "tard" is a social friend of the executives...so basically his screw-ups/laziness get totally ignored, and the rest of the dept has to clean it up.
I've been at my job for about 7 years, and it's good. Last year, has been rough because of "tard". Multiple talks w/ management, 1 talk with "tard", and I'm still at the same place.
Only option left for me is to leave, or put up with it.
If I didn't have 4 kids,wife,mortgage, I'd tell them exactly where to shove this job, but jobs that pay this well, for what I do, are few and far between. Also, I've got some 401K built up, 3 weeks of vacation a year, some small perks.
But basically, staying here is the "less of 2 evils".
So, decide which evil is "bigger" and KILL it. Either leave, or stay....but make the decision and commit to it. Trust me...you will feel the pressure ease, and you wil be able to relax more, and not get that "knot in the stomach" feeling whenever you have to deal with Mumbles.
And if you decide to leave, take plenty of time to make sure "Mumbles" knows exactly why...
Good luck, and be true to yourself.