I just measured and I have a short cage, 55mm. My gearing is 34-50 and 11-25. That looks like 30t chain wrap.
Previously I ran 12-25, resulting in 29t chain wrap. Does 1t really make that much difference? Would moving to a medium cage help?
My chain length is set by running large cog to large chainring plus 1 inch. I could add a link (next time I change chains).

I played with the worm screw and I can modify the angle of the RD, but it doesn't appreciably change the distance between the idler wheel and the cassette.