That's correct, don't use the W7 on the PPF as stated.
I would try using a 70-30% solution of Water(70%) to IPA (30%), apply a small amount to a cotton pad and apply to the tar for 10-15 seconds.
After applying the IPA solution, I would then use a microfibre towel that has been sat in some hot water to hopefully remove the tar.
You may need to repeat this process until it has all been fully removed.
In essence, the IPA solution is going to help remove the tars bond to the PPF and the hot water should hopefully encourage the removal due to the heat element.