Mel - I would suggest you remove Tequilla from the tank and move him to the fridge.
I would add the light salt solution to his water in the fridge for just a day or 2 day then return him back to fresh water in the fridge.
If you see fungus start on his nipped gills then give salt baths. (2 teaspoons of salt in 2 liters of water for 10 - 12 min) Use the same temperature water that he is being kept in.
I would leave him in the fridge until he is eating again. Keep in mind the fridge can't save all axolotls but it isn't going to hurt him.
You do not need to punch holes in his container unless you feel you have to. Keep them smooth so if he jumps into the lid he will not cut himself. An ice cream bucket works well.
The toxic chemicals he has been exposed to along with possible disease from the new axolotl along with the new uncycled tank, and bitten off gills have stressed him badly if nothing else. He needs time to heal.
Please read this article on tank cycling
http://www.caudata.org/cc/articles/cyclingEDK.shtml
If your tank wasn't cycled and is 3 weeks in your axolotl has been possibly subjected to ammonia and nitrite. Both are not good for him, and could be contributing to his not eating.
If you need more information on tank cycling use google and you will find hundreds of articles.
Once your axolotl is out of the tank do not clean out your tank by removing water, instead I would recommend you go buy a fresh water test kit that will allow you to test for ammonia, nitrite, nitrate and ph. The kits that use drops have worked for me better than the dip strips.
Your tank will not be safe for your axolotl until it has cycled. The only way to know it has finished cycling is to test the water and watch it cycle through testing.
If you have the water from your old tank, I would add it to the new tank plus any ornaments and some of the substrate. If the old tank had a filter that hasn't dried out I would put that on the new tank as well. These items hold good bacteria and will help your new tank to "cycle".
It is best to keep all your messages about the same incident in the same thread. It makes it easier to follow for new people with a similar problem or for people who are interested in seeing how things turn out.