For a proper grenade-in-the-portaloo departure, I would suggest the following amendment to 2, assuming that there's a D, E and F (or even G, H , I, J, K, L and M if your band is a ludicrous monster like mine) and that they're not party to the skulduggery:
2: Leave the toxic environment completely, but throw that grenade on the way out - "I am leaving the band. For those of you who don't know, there is a secret plot to bin one of you and there is an audition already arranged for the replacement. That's is appalling. A band should be like a marriage - if it's not working you end it. Not try out a side piece first"
D to M will now be wondering which one of them is the backstabbed and who the backstabbee is. Kaboom.