Stop kidding yourself - get rid of the poly.
I've seen the difference it's made among both older and younger players with rather strong games and "arm-friendly" racquets. If you've had any previous elbow issues, then it's probably wise to assume that you're simply more susceptible to arm problems than some of our pals who do fine with that string.
If the cost of re-stringing more often gives you pause, I'd say that your #1 priority should be keeping healthy so that you can keep playing the game (dump the poly). Consider getting a simple stringing machine and you'll never have to worry about the either expense or inconvenience of using more fragile string again.