...Autodesk 2010, which is one of the engines used to create this game, is one I use to do my drawings as an electrician... If that's not exactly "third party development", I'm not sure what is. Lesson learned and moving on.
I don't know much about trouble shooting this game yet, so I can't help you with your problems, but I did want to comment on this, as it is quite far from reality.
First: Autodesk is company, not a game engine. This company happens to own virtually all 3d software used in the industry. The one you mention for drawings as an electrician is probably AutaCad along with some of it's suites of add-ons. Autodesk also owns both 3DS Max and Maya, the 2 main programs for game development and even 3d effects in movies. However, neither of these is a game engine, as Autodesk does not have one. They are for creating 3d assets such as character models, rigging, animation, effects, etc.
The engine that Divinity2 uses is Gamebryo: The same engine as Civ 4, Oblivion, Fallout 3 and many other top games.
The main thing you should take away from this is to always patch first.
I hope someone can fix your problems, and you can go back to enjoying this game as you seemed to have before the problems started. Good Luck