First of all let me reply to your plight by saying that all 'Ministers' have much of the same situations from time to time. But with that being said, I think one has to ask oneself this; am I 'Minister Of Music' or simply just another musician playing for some church? There is a big difference. Ministers are called by God (well supposed to be at least...), and if believe that you were called by God to minister in music, then you should be just that--- a Minister anionted by the Holy Spirit. That means wisdom, patience, long suffering with the flock that God has put in your hands, where ever, who ever and however they may be. Just as our Lord and Savior Jesus Christ was longsuffering with his disciples (they in many instances did not understand what Jesus was teaching them), and many times he had to correct them and even rebuke them, he never 'resigned' on them even to the cross. And to this day He doesn't 'resign' on us through all of our shortcommings. As a Minister the saving of souls and deliverance is of uttmost importance, to a musician simply 'sounding good' is all that is important. Now, as a Minister of Music, yes sounding good (giving God our best) is very important, but not to point of forgetting what we are really there for. So, you may consider seeking God to get the wisdom to lead that others may follow your instruction, but remember that takes an anionting from God if you are truely chosen to Minister. All musicians are not Ministers.
I don't know the size of your church, but basically what I have done ( as alot MOM have done), I choose the best and more dedicated vocalists and form a praise unit apart from the general 'choir' and then work with the rest according to their ability. This means that selections that the general 'choir' can handle and sound somewhat decent on, well they do those songs, but the praise team does the more demanding and challengiing songs. It works out well for us, with the praise team, the better vocalists and musicians don't get bored, and the least talented members of the general 'choir' are not pushed beyond their capablity which can foster resentment.
Please, don't get me wrong, I am not suggesting that you stay anywhere you are not confortable, but I am saying let your reasons be spiritual, not merely musical. Unless of course you are just a musician and not a chosen Minister, in that case it doesn't really matter. Grow in Christ and trust me, you will grow as an artist. God has called us all to excellance, but only after we seek him first (not the music first) and all things will be added. I know because it has happened in my life and Ministry.
So hang in there my brother, and may God guide your way.