Hi Ari,
I am the Shane who you have been in email contact with, it will be easier if we all continue to work out the issues on this thread so everybody can stay up to speed.
Right off the bat I will just weigh in on the substrate issue briefly, I do not believe Eco Earth to be the cause of these issues but it certainly could be making things worse in this case. Any loose substrate can cause or exacerbate issues when husbandry is not spot on and the animal is not well hydrated and healthy to begin with.
I have seen the images of the poop and now of the setup and am confident there is digestive issues of some sort at play. I also feel that this is very possibly being caused by improper heat provision, to solve that you are going to need two things, a thermometer, either digital or infra-red and a thermostat to control the heat being put out by the mat you have.
If you let us know where you are living we can perhaps recommend a good place to buy these things. They are quite affordable for most people but you are going to need them for certain, I'm afraid there is no getting around it.