Potassium and Magnesium From iHerb

Hello,

I successfully finished 3 days fasting with salt only. Now I want to try 5 days and then 7 days.

Potassium: https://www.iherb.com/pr/now-foods-potassium-citrate-pure-powder-12-oz-340-g/69741
Serving size 1/4 tsp, 448mg, which means \~2 tsp needed

Magnesium: https://www.iherb.com/pr/doctor-s-best-high-absorption-magnesium-100-chelated-with-albion-minerals-100-mg-240-tablets/16567
Each tablet is 100mg, which means 4 total for fasting

1. Are these good supplements to order?
2. Am I right about amounts?
3. Any better ones from iHerb?