How to salvage a totally nuked cast iron dutch oven?
Simply put you nuked your food. The temperature got too high too quickly and the moisture in the pot boiled off faster than it could be replaced by the meat, and then all the fat and juice plus the meat in contact with the pot's surface got charred on. Fat from the meat got stuck all around the pot and adhered, and the heat was intense enough to blacken the surface of the meat. It sounds like temperatures were far higher than 450F.

The good news is that there's probably nothing wrong with your dutch oven that you can't fix with some steel wool and good old fashioned elbow grease. The blackened stuff at the bottom is simply charred meat, I don't imagine the metal underneath is damaged, so scour it clean and re-season it. The lid got covered with lots of fat which has yet to come off which is why it's sticky, lots of dishwashing liquid and more scouring should fix that too. Personally I've never had any luck with boiling or baking char off pots and pans. 

My own experience with dutch ovens is that they work better if you have heat coming from all around rather than just at the bottom. If you only have bottom heat it has to be more intense to heat the whole thing, and as campfires are not an exact science it's easy to accidentally char the bottom. Having less intense heat on the bottom and putting a shovelful of coals on the lid gives a nice even heat.