Hi, KatsuoHana, I am still working on the M3K. Thanks for trying out g3290 and taking the initiative... did you use the latest patchset 22? IIRC, the main change there is the PLL/system clock initialization. I've got some changes locally which do the same thing in a better way, but I need to clean them up a bit before I push it out. I'll try to get that done this weekend, judging by your testing it should fix the hang on boot.
I am not surprised that things don't work well on g3290 because it has a lot of slowdown due to the debug code I added. Hopefully a proper build with fixes included will work smoother for you.
Play/pause on the WPS is indeed mapped to both the touchpad and physical button. Keymaps are currently not ideal right now, but the button problem you described is more the fault of Rockbox's default settings. This is not fixable by keymaps, or at the driver/firmware level without introducing other gotchas.
If you enable "Advanced Key lock" (aka. softlock) and turn on Autolock On, Always Autolock, Exempt Volume, Exempt Play, and Disable Touch in the submenu, then you get something approximating normal screen locking -- the touchpad turns off when locked, and you can still play/pause and control the volume.
IMO, the way to go is improving softlock and making it more consistent, then enabling it by default on the M3K. I'm sure other touch-enabled players would benefit from this too.