Seeing as how my ground water is like 70 year round, I pitch in the low 80s everytime. I haven't had a problem with stillborn yeast thank goodness. The only dry yeast I've used is Safale, and I know different strains attenuate to different FGs. I still need to get a prechiller to bring the initial temp down though.
An FG of 1.015 is pretty much done. You might be able to sweak some more out of it, but I wouldn't worry until your next batch. I do suggest waiting a couple more weeks to really start draining it. You'll notice the flavor changes.
If it resembles beer, you win. :cross: