Question about when to add nutes, and about ppm????

Ok to keep it simple lets just say I want a ppm of 1000. So I have a 40gal res... I fill it up with 40gal of plain water add my nutes till it's at 1000ppm, adjust my ph to 5.5. I have that correct so far right? Ok heres my questions..

1-The next day if it was 1200ppm I add plain water until its at 1000 again and next feeding I use less nutes like around 800ppm or keep using 1000ppm?

2- If the next day it was at 800ppm do I add more nutes until its back up to 1000ppm or do I only add nutes once a week?

First off, the plant isn't going to curl up and die if the range varies a tad. I'm guessing that you have picked an arbitrary number based on research and are trying to hit that. while that is admirable you may be better served by watching your plant and watching what it tells you. I would top up or down like once a week if you are getting some creep up or down. Basically figure out what is working when you add a certain amount in the beginning and try to make that same dose again every week. The ph would be more important on a daily basis in my opinion. Not a real expert though so take all this with a grain of salt

Alright so your saying add nutes to 1000ppm (again just an example) then dont add anything all week? Even plain water?

The plants are only gonna eat what they want no matter what ppm you make it. I normally try to find the ppm that they eat at the same rate as water. That way when the water goes down the ppm stays the same not creating risk of nute burn. If the water goes down and the ppm goes up then I would feed them less next time. If the water goes down and the ppm goes down I would feed them more. Sure you can run them at 1000 ppm if ya want and they might do ok but why put more food in the water than they want, esp if your gonna just dump it later. So I think you were on the right track with dropping it down to 800 and check again when water drops.