Seems like the PO really neglected the drivetrain
I'd start with fluid changes on everything, that may help your transmission. Pennzoil Synchromesh or Royal Purple have given good results. What happened to your first t-case?
As for your supposed head gasket leak. Some coolant leaks can be in the form of vapor and won't give you any real warning signs. This can be confirmed with a special UV light typically found at a shop. I'd recommend doing a compression check on all of your cylinders, it may help verify all is kosher.
Definitely clean your TB and sensors and check if that helps with the stalling. 114k seems wayyy to early for a rebuild even with a little abuse and neglect