So the max 100Hz is likely the cable/dongle you're using. I found that using a USBC/Thunderbolt straight to displayport will get the full 144Hz out of the monitor. If I use an adapter with HDMI + HDMI cable, it doesn't do more than 100Hz. Likely a hardware limitation with the resolution of the display + cable type used though I'm not completely aware of the specifics there.
As far as you mentioning "same problem" do you mean what I'd said above? To get it to come back on, disconnect absolutely everything including power from the monitor and give it a minute or so and it should come on fine.
In terms of moving forward, what I did was disable any kind of power saving on the monitor and the Mac. If I recall, as long as I was the one to specifically turn the monitor off and the Mac didn't let itself go to sleep, it would always turn back on.
As I mentioned in my previous post, the exact same behaviour was replicated on an entirely different ultrawide, so assuming you're on a Mac, it's almost certainly the Mac that is the issue, not the display.