Ok, You need to use the teflon or silicone lubricant recommended for rubber O-rings. Petroleum products destroy the rubber.

I am fighting a bloom as well, but because my liner is old and I don't care about bleaching, I've got my FC level a lot higher than the 15ppm recommended.
I wouldn't worry much about going over by a bit, even to 24ppm, because it will come down fairly quickly and it's worse to be UNDER 15ppm than over.
It's not certain how much over the recommended shock level you can go, or for how long, before you risk bleaching the liner.