Hey Bro, glad to see that you have stumbled onto my Q/A. Your story is quite extreme. Low test levels can certainly contribute to difficulties with fat loss. Still, in itself, it will not be the entire answer. Steroids don't directly have a strong fat buring effect but being at optimal levels can make a huge difference in your ability to make progress. The biggest factors at play are going to be your diet, cardio and rest. Even with steroids, you won't make progress, if these things aren't in order. For a healthy individual, it takes a lot of suffering to get in great shape, and there is a good chance that someone like yourself is going to have to work even that much harder.
As for using gear and understanding how to use it, the first suggestion I am going to make, is to hang around my QA and read as much as you can. No matter how detailed I answer your question, I'll never be able to break everything down for you in one reply. There is so much to know, in order to be safe and get optimal results. It's taken many years to gain the knowledge I'm sharing here, and I'm still learning to this day!
For HRT dosing, about 100-200mg of Test Cyp is standard. Everyone is different and the only way to know how much you need, is to have lab work done. If your Dr is not able to write you the script you want, maybe she will at least monitor your lab work and keep you in the safe, upper end of normal. If she isn't willing to watch you, find another Dr that will. HRT is a life long commitment, so you want to know that everything is at the right level for the long haul. The goal here is an improved quality of life, right?! Along with the test, you will need an AI to control estrogen. Arimidex at .5mg 2x wk would be a good place to start.
Once again, I cannot stress how important diet is going to be in this process. You can take test and have little to no improvement without the right plan. Feel free to contact me, here at the Next Level Nutrition header in the QA if you are interested in working on a plan. I am 100% certain that you can make vast improvements if you have the willingness to change.