I can add that I have had challenges acclimating Amano shrimp to my 30 gallon aquarium. Based on my own observations to date:
You had mentioned temperature, Ammonia, and Nitrate. While these are important, I can add that JUST as important are additional water chemistry paramters
the next time you go to a store to purchase shrimp, request the pH, KH, and GH readings of the current tank the shrimp are in at the store. If you do not know what I am referring to, purchase a pH KH and GH test kit to have at all times at home and to bring to the store. You want to know what the pH, KH and GH readings are of the water in your tank as well as the readings at the pet shop tank the shrimp are in.
I have spent hours placing purchased Amano shrimp into a Tupperware container on top of my aquarium so the water temperature in the Tupperware container matches the temperature in my tank. In addition, I shut my aquarium light OFF for 1 full day to reduce stress on the shrimp. I place some of my tank water into another container at a level above my tank to allow a siphon to occur through an airline hose and valve set to online drip into the Tupperware container with the shrimp in it at a rate of about 1 drop every 5 sec. Shrimp are EXTREMELY sensitive to pH changes and/or drastic hardness changes. I have found based on experience that your home aquarium should really have nearly the same pH or within 2 steps that the store kept the shrimp at. By steps I mean if the store water is at 7.6, and your tank is at 7.2, I would consider it 1st step drop to go from 7.6 to 7.4 and a 2nd step drop from 7.4 to 7.2. I have never had success acclimating shrimp more than 2 steps of pH change in one day. I really think you will have the best chance of acclimating shrimp checking on the store water ahead of time and getting your tank nearly the same pH, KH, and GH if possible. You do NOT want to change the chemistry on the same day you introduce the shrimp but will want the home tank water set and in equilibrium at least one day prior.
Example: suppose your pet shop has pH - 7.8, KH - 8 and GH - 20 and your tank is at pH - 7.4, KH - 6 and GH - 15; I would assume the chances are good that as long as you perform an online drip over several hours and do not introduce the shrimp into your tank until the Tupperware container basically contains nearly almost all your home tank water (remember to keep your tank light OFF 1 full day) to better allow the shrimp to tolerate the stressful change from store water chemistry to your water chemistry. It is ideal if the water chemistry is nearly the same at your home that is at the store or where the shrimp were bred. Performing a proper acclimation takes time to have the best chance. Also be careful when putting them into your tank as well since they are fragile.
For my next attempt, I am purchasing from The Shrimp Farm which specifies what their water parameters are which seem to be very close to what my chemistry parameters are.
Good luck on your next attempt at acclimating shrimp into your tank. See some helpful links below.
<<<==== this is an excellent link! only thing I would change is make online drip rate slower and have your tank light OFF
<<<<===== also excellent link