Question: Revolutionary or stupid? Protein powder.

I have this possibly brilliant, revolutionary idea to save my axolotls life. But it's so obvious that I should have heard of it by now, and that does worry me. Is the idea stupid after all?

Here's what:
My juvenile axolotl has been in the fridge for the past 5 weeks. He has not eaten and he's getting dangerously thin.
He's in there to slow down his metabolism so he can rest and his wound can heal in peace, with no bacteria festering.
The downside of this is that his metabolism, while being so slow he does not need to eat frequently, is too slow to eat at all now. So at this rate, he may starve before his wound has closed. The wound would also close faster in warmer water (=higher metabolism). I've observed this with his tank mate. Out of the fridge, the wound closed way faster. But his wound wasn't as serious.
However, warmer water would cause bacteria inside the still-open wound to fester so fast he'd die within hours or days.

So I can only hope the wound closes inside the fridge before he starves, and I can put him in warmer water and feed him then.

But that might not happen.

But then I remembered: you are not supposed to add any chemicals to your axolotl aquarium (like anti-algae, liquid filters, vitamins,..) because the axolotl absorbs these chemicals through the skin. But doesn't that mean that he would absorb protein if I were to mix protein powder in his water? That way he would not have to actively eat. It would be like an IV drip that he is swimming in. Any thoughts?

Axies won't absorb protein powder through their skin. The molecules are too big and they are not water soluble. Protein must be eaten to be useful.
Have you read the tutorial on force feeding? If you can get something inside your axie it may help his recovery.
Alternatively take him out of the fridge but keep him cool - maybe 12-15C - and he may get his appetite back.
But I swear by waxworms for tempting an axie who has lost his appetite - can you get hold of some maggots, butterworms or waxworms? Maybe he needs somethig different to eat.

I strongly advise against adding protein to the water. You will soon have your axolotl swimming in an anaerobic bacterial broth, bacteria will eat the protein, use up all the air in the water and create a putrid soup with a dead axolotl in it.

Is the axolotl in the warmest bit of the fridge (often front top shelf if the fridge has a separate freezer compartment)? Putting glasses of water at various spots in the fridge or house and taking their temperature may enable you to locate a slightly warmer but still cool spot. I appreciate you are not in the best climate (Google says 30C outside: Here in Wales it's a nice sick axolotl friendly 11C so I have lots of cool spots, it's me who feels uncomfortable).

I would skip using maggots on a fridged axolotl, at 5c they have problems digesting them.

5 weeks is a long time to be fridged. If his wound hasn't healed in that time, I don't think it will.

Can you raise his temperature up to about 10C? At that temp he should be able to eat, and it's a bit safer than bringing him all the way to room temp.

The temperature is between 10 and 12° Celsius, has been all the time.
Thanks for clearing that up about the protein. Did sound too good to be true.