you can get a cortisone shot for the tendinitis in the elbow. it will only give you relief for a while if you keep aggravating it, rest is the only cure. I don't know your age but I can't see using a kayak as the primary vehicle when you fish as many days as you do. watched your video yesterday and said to myself "lot of work, is he in pain".
If you must fish why not use spinning gear with circle hooks? You can cast sidearm while keeping your elbow straight and the circle hook does not need to be driven home...
I know what your going through I have tendonitis in both shoulders and need to cast sidearm. The problem with the cortizone shots are that they break down the muscle tissue if you get them too often. You may want to try it once if the pain is constant, it should relieve the pain and give you some comfort till it heals itself. I'm sure your doctor will suggest physical therapy also.
Rest it and ice is the best advise...