Ditch the chalk. Only needed for dark beers to increase pH. Martin has said before that it doesn't even work unless you dissolve in water with co2. I could see needing the lactic with such a light colored beer, but if you are between 5.4 and 5.5 without, I'd say skip. Chalk and lactic are actually counter productive in your case.
You should be fine with gypsum and a bit of calcium chloride. I'll play with the numbers when I get to my computer.
And if you are using RO, acid doesn't need to be added to sparge. You shouldn't add chalk to sparge anyhow as it won't dissolve.
Read the first tab. It helps a lot.