Re the tennis elbow, mate I had it bad from guitar, it was on the left arm thumb side of the elbow.
Painfull, if it hit a doorway it could send you thru the roof.
I stopped playing and wore a compression strap,cured.
The strap had a lump or cam you place on the painful tendon then wrap it tight.
It stops the tendon extending too much, giving it a rest.
Now I have it on the pinkie side of the elbow left arm, some call it golfers elbow.
I reckon it's from holding a rod too long, but it could be from catching too many fish.
Rather than going under the knife, try the strap (chemist shop), cortisone injections, or switching left to right.
It's not uncommon amongst fishos.