I'm sure warming the fluids, both the bag and line, will make a big difference in how Max accepts the fluids. It will take a few sessions before he realizes it isn't uncomfortable any more, of course, but then he will be "normally" antsy about it. Watching your cat's behavior/reaction and trying to assess what they are telling you can be a very difficult translation job. I thought Diego was hiding from me because he was already in some pain when it was time for his meds, which are given through an oesophageal tube because the pain is in his mouth, but it finally dawned on me that the pain meds (given always in warm water) might be hard on his stomach. Now I give about 20cc of well warm watered down baby food first and he's started letting me scoop him up more easily and will relax and purr while the procedure is done. Sometimes you feel so dumb that you didn't figure things out sooner.

I hope you can get Max into a plateau time, that can last for many, many months, where he is coping with treatment and has a fair quality of life.