as I don't know the new Canon mirrorless cameras, I'm afraid I can't help much, but I'll try.
1. things blinking usually mean that that feature is not available for some reason. so ETTL blinking could mean that ETTL flash exposure is not available and that you should switch to manual mode 'M'.
does ETTL blink when you set the camera to manual mode?
2. is 'auto power off' enabled? could it be set too short?
I don't know how well/bad do ETTL work nowadays, so I always work using the flash in manual mode. that also helps to realize what one could be doing wrong.
the best way to avoid white balance 'WB' problems is to shoot RAW as you can correct it in post. if you don't want to shoot RAW, then the first step would be setting the WB to Flash. if you don't like the result, you could try creating a Custom WB for your flash. the last option would be to take some test shots changing the value of the K mode in the WB until you find the one that you like the most. again, shooting RAW could be the easiest way.
about your original post: I don't know if you already know this tip, but when using manual focus for macro, it can be useful setting the focus to whatever magnification you want, frame the shot roughly and move your body back and forth until you nail the focus. with mirrorless cameras, screen magnification helps a lot when doing this.