So going back to the original question of TDS for shrimp, that's not what would concern me with your RCS right now. You need to bring those temps down to under 76F, preferably lower 70's..
TDS isn't really useful for telling you what is in the water. You could be targeting 240 TDS for RCS, but that doesn't mean you have a proper dGH. GH (mostly made up of Ca and Mg) is the most important thing for shrimp.
To give advice on how to use TDS to evaluate when to do water changes and such, we need to know:
1) What are you adding to your water that is causing the TDS to be so different from tap?
I have even lower TDS from tap here in the Portland area, so I have to add CaSO4 and MgSO4 for my shrimp (and plants).
2) How are the shrimp doing for you? Any deaths, breeding, etc.?
I shoot for 7-8 dGH for neocaridina such as RCS. I firmly believe KH doesn't matter to them as long as it stays stable. TDS is similar - keep it somewhat stable.
Generally, we get parameters stable, measure after water change, then do another water change once it creeps up high enough. What high enough is to you will be based on what you are adding to the water and the behaviors of your shrimp.
I don't subscribe to the limited water changes for shrimp methodology, and it's highly subjective in my mind. I drip a 50% water change each week for my shrimp tanks, and I only use TDS to check that nothing is creeping on me.
I've managed to cool down the tank temperatures to about 75, I don't use a heater because my room gets so warm, i think the temperature creeps up at night when I close the door to my patio and the room warms up over night, that's what probably what brought my tanks temperatures up. After cooling down my room the temperatures drops closer to 75 so that is less of a concern for now, though being ever vigilant I may have to actually hook up the ac if the temperatures remain high throughout the day after leaving the door closed at night to run some ac at night. So far the only things that I am dosing my tank with is flourish (about twice a week) for my plants and the "just right" water conditioner that I use. So far there haven't been any deaths and the shrimp seem pretty active and are eating well (when my snails decide not to be jerks and surround the food). I'm currently feeding them sinking pellets and on occasion spirulina powder, with plans to get some organic cucumber/zuchinni (spinach if they have it) from the local farmers market to boil and feed. I haven't noticed if any of them are breeding yet (the snails are breeding like rabbits). I just added prodibio aqua growth substrate and did a water change, vacuuming the substrate during the addition to clean away some leftover gunk that had hidden. Away in a corner.
My current readings as of now are:
PH - 6.6-6.8 (I attribute this to the prodibio soil?)
NH4 - 0 ppm
NO2 - looks like it's running closer to 0.25 ppm but not quite there.
NO3 - looks like it's possibly between 0 and 5.0 ppm but not quite either.
Gh - 3
Kh - 2
TDS - 130 I've measured this whenever I've done a water change so it seems roughly about 130 (sometimes a bit less after a water change) is a normal parameter for my tank after dosing etc?
Temperature - 77
From what I understand I don't want any NO2 in my tank but shrimp can tolerate some NO3 (which plants need) correct? Or would it be better to eliminate both NO2 and NO3 in my tank? (Could these numbers creeping up suggest I need to clean my filter?) What would you recommend to bring the GH up in my tank to make it better for the shrimp? Since I scattered my plants around and made it more jungle ish in my tank the shrimp seem to be much happier after adding the new substrate and seem to be a bit more active than they were previously. Is the PH fine where it's at now or will I need to add something to bring the pH back up? I appreciate the help! I'm a beginner to shrimp and want to make sure I'm doing my best to take care of the shrimp!