I am sorry no one has answered your question yet. I work at in the field in the day and answer questions here at night.
If your steering clutch valve is not working, that would cause the tractor to require greater effort to "force" a turn.
What I see the most often is the small roller bearing fails on the valve stem and the cam cannot open the valve enough to release the steering clutch.
You must never adjust the linkages, all adjustment is done to the brake band only. If a pedal is not working, something is worn out.
I would remove the right valve and replace the stem bearing. Also, replace the actuating cam bearing and its shaft if they are worn.
That should get you back to normal operation.
The only trick to this repair is to disassemble the valve and pull out the small roll pin that acts as a guide for the stem. This will allow you to turn the stem and knock out the roller bearing pin. Note: these are small parts and a little wear will cause a lot of trouble.
If you need further help, please let me know.