200% dose would be 2 times the dose, so 10ml for 50g. 1L of excel would probably kill just about anything, fish, shrimp, plants, etc.
As for plants with excel, I have read that plants that are sensitive to excel can be acclimated to it over time. Starting with a small 25% dose for few days, then moving to a 50% dose for a few days, the 75% for a few days, and finally getting to a 100% dose after 2 weeks or so. Of the plants you listed, Vals are the only ones that would mind the excel, so maybe just rehome the Vals. The moss and java ferns should be fine with it.
As for shrimps with excel, there is very mixed reviews on using excel with inverts. Some say they use it all the time with no problems. Others say it wiped out their entire tank. Also, with CO2 gas injection, PH swings can be a problem for shrimp, so you want to be sure to have a consistent PH. I have read about many people waking up in the morning with a tank full of dead shrimp due to PH fluctuation over night. With the excel it doesn't effect PH so it would be safer, but many report deaths of shrimp with excel use. It scares me to use on my RCS tank so I don't. I do use it on my community tank with ghost shrimp and they seem unaffected. Although ghost shrimp are tanks, I think I could set off a nuclear bomb, and they would still be scouring the gravel for debris and doing there thing.