The guttural sounds and pronunciations are important to properly reverse the spoken hebrew it is reversing.
However, as HPS Maxine says, just do the best you can.
If it hurts your throat, better to make the pronunciations slightly softer to accommodate yourself, than to hurt your throat by forcing them.
The most important part is to infuse your intention into the RTR, together with the pronunciation.
So long as your intention is as strong as you can make it, and you follow the pronunciation best you can, it is effective.
I would advice to practice the guttural sounds and learn to speak them without straining your voice, as the power does amplify when you perform the RTR's with exact pronunciation.
Watch a few Dutch language tutorials for example on how to pronounce certain guttural sounds that are common in the RTR.
The Dutch language has a bunch of sounds similar to it.
Hail Satan!