According to Them That Know the sweet spot for a KF is about 1.5 ohms. I run mine at 2.5 ohms and am very satisfied. No, all the kids on the block don't point and OOOOH AHAAA when I stroll by, but I'm happy.
Your istick is a regulated mod and has adjustable wattage. Your KF likely has adjustable airflow. Just tweak your KF to make you happy.
Neither the KF or the istick were designed for sub-ohming