You have a unique situation hunting stubble fields...Requiring constant height and momentum of the coil adjustments..Even with a light rig like your Tek...
I will say, Tennis Elbow is a common issue in this Sport...A fellow soon learns to modify their body mechanics to overcome or otherwise minimize its impact via the use of various forms of gear...
I also swing wide and fast, but not in stubble, mainly on flat beaches or sports fields......so any of my learned methods will be of no use to you...I did learn to concentrate on the body mechanics for a while...Using the stronger muscles in my body so as to not focus the stress on the weak links like an elbow joint...
I swing with my whole body, and allow a steady momentum of the coil to power itself...Also, how tight you grip the handle is important...too hard a grip stresses the tendons...just the finger and thumb like holding a pencil, or a paint brush, nice steady swing...concentrate on an alternative way to hunt your situation, you will come up with something that works comfortably...GL and HH!
You might try a 'drag' method of hunting rows instead of a swing? you know, just walk in one row and sort of 'drag' the coil along in the next one? No swinging at all! I do this on big stretches of beach right in the riffle trough at the water line with great results...I troll that coil right through the edge...