Matt, you really must have a pressure canner to safely can meats.
I have done a lot of primitive cooking over coals, and you could use your pressure canner directly on coals as long as you kept a very close eye on it and moved it to hotter or cooler coals as needed to keep the pressure right.
I use a gas stove for all my cooking, which is the same thing the Amish do.
The seals on meat seem to seal better if you cut off excess fat before you can the meat. However, prior to Y2K, when I was concerned about getting enough calories, I canned fatty meat. I lost a few jars, but most of them sealed. I ate the last of that batch in 2002 and it was still good.
I also canned beef tallow (fat). There are two ways to do that. You can just fry the fat out at a low temperature. Or you can boil the fat, put it in the refrigerator, let the fat rise to the top, then clean it up a bit. I run all my hot tallow through coffee filters to get the particles out.
What is left is pure white tallow--good for cooking or making candles or soap.
Edited to add that you do not put tallow in a canner. It is hot enough that you just pour it into jars, seal them, then invert the jars for several minutes. That is all ther sterilizing that is needed for tallow.
Hope I answered your questions, as I'm not sure I understood them all.