Having played in Church for over 40 years using all sorts of guitars and banjos, I appreciate your problem. At the end of the day its really not worth risking damage to an instrument just to accomodate a different key. All the advice about using a capo is good and i suggest that you try finding the right one for your guitar and using it properly. Also. if you can already play most of the main chords (c.D G etc) it shouldn't be too difficult to learn a few more. I have also always had problems playing barre chords and avoid them if at all possible. There are all sorts of "Cheat" ways of playing a lot of them using only a barre on 3 or 4 strings - well worth learning. The other point worth making is that from experience I have learned that a strong vocal lead in the music group singing in the key which you have decided on will usually have the congergation in tune with you. You should lead the singing, thats what you are there for.
Persevere with your efforts and good luck
Pete