Carriage house stablization project
welcome to the forum!
You may not like my post but here goes ..... you can see what you have, we cannot. the causes of your issues can be many, the cause could be rafter thrust from a sagging roof that may need a structural ridge beam. As the roof sags it pushes on the tops of the walls.
I understand money is tight, but I highly recommend contacting a local professional engineer to evaluate your structure and prepare a plan of action. You can "try" various fixes and spend money on them only to find out what you fixed was not the cause. Would hate to see you waste money and time and still have the same problem. Depending on what your engineer comes up with you may still be able to do the work yourself, or with some knowledgeable friends, but at least it would be done properly the first time.
The money you pay a professional engineer will save you money and time with the repairs.
Just my humble opinion, good luck!
"You get what you pay for, and sometimes free costs more!"