Olympus Flash Exposure Compensation

I have searched the forum and know this topic has come up many times before. I am getting inconsistent results, mostly under exposure by 1-2 stops, particularly when using as a bounce flash. I am confident it's 90 percent user error. Increasing the FEV only partially solves the problem. I wonder if my flash is too weak (MEIKE 320)

I was wondering what metering mode and exposure and exposure compensation settings everyone uses. I am also wondering if I should just give up on Auto ISO. I use Fuji as well, and while I have other annoyances with that system, I fine the Fuji does an excellent job at metering and adjusting flash output, and in general increases ISO a lot more willingly in Auto ISO than Oly does to prevent under exposure.

I'm using an EM-1 usually at shutter speeds 1/125 to 1/250 and f2 to f4.
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Family Man/Amateur Photographer