What's your usual PG ratio, and were you getting harshness from that? Were you at the same nicotine level?
Reducing PG may reduce throat hit, yes. It may also as others have indicated, be a particular flavor that is making it harsh. It's also true that 9 is on the high side, but not insanely high side.
If you like the recipe otherwise, I'd say try making some small tester bottles:
1) with less PG
2) with less nicotine
3) with less flavorings.
If you do that and let them steep for a bit (lack of enough steeping can also cause harshness, BTW) you should be able to identify which factor is the culprit, more or less.
Then, you can take what you have mixed NOW and fix it. The good news on fixing a failed mix is, well I have learned more about DIY by fixing my failed mixes than by enjoying the ones I'm lucky enough to enjoy right out of the gate. I almost NEVER toss a mix before messing with it (chocolate milk was my one exception, it was SO vomitous I really did not know what to do).
But, you'll be able to change whatever ratios you need to with some planning ahead, a good recipe calculator, and some patience, as, say it's the nic level, and you need to reduce it, you will have to add VG, flavors, and nic at the precise ratio you'll need to dilute the mix by with your VG.
Anna