OMG, you are going thru hell and back. I am sooo sorry.
I pray that poor little Aiden can finally be diagnosed correctly and get the proper medication or whatever it takes to get him well again. It is too bad that vet can and do charge so much because they know that somehow we will come up with the money for out babies. They should offer discounts when the billls reach a certain point. They are vets so they love animals. If they loved animals that much then why would they withhold medical treatment that might save a pets life if the parents couldn't afford it. Sorry, it really upsets me to think about it.
Maybe the vet will work with you. I know you'll do whatever it takes to get Aiden well again. Your posts show how much he means to your husband and you. I also hope your husband is doing better. Please take care of yourself and him so you will be there for Aiden so he can be a healthy little puppy again. Prayers for a simple solution to all this.