There is no question of a devotee becoming a sudra if he does certain work. No, a devotee is never a sudra. He is transcendental. Because their activity is done in transcendental loving service unto the Lord, it is all on the transcendental plane, brahma bhuyaya kalpate (BG 14.26). You should not quit your present job, it is good service to Krsna. Although you may be working hard, you are always working for Krsna; so do not be confused about your position and never forget Krsna in any circumstances.
Your father came to see me recently in Bombay. He talked with me for hours and took prasadam and enjoyed. He looks strong and healthy and I think he is now cured. Henceforward you can send all contribution to the above trust fund.
I know you are doing your work for Krishna, so continue it, and send me information on how you are doing.