For 20 gal. I would start out with 4 tsp. of Equilibrium and then measure GH. I predict it will be about 6 dkh.
For KH I would start with about 1.5 tsp. of potassium bicarbonate.
I wouldn't worry about pH, and TDS is going to fall where it will. It should be close to the 200 number you want, but with Equilibrium and potassium bicarbonate producing a GH of 8 and a KH of 4 I don't see why you would want to independently alter TDS.