Single-button mouse and X keyboard: solved
I finally managed a mouse to behave well by kernel argument
'adb_buttons=0x67,0x6f' (keycodes of F11 for middle button and F12 for right
button emulation). It works in gpm as well as in XFBDev.
BTW, is it right that left and right Ctrl's, Options's have same keycodes?
I also tried XKB extension in XFBDev (I need Czech keyboard), switching
keyboard ('setxkbmap -keycodes "macintosh(macintosh)" us' and '... cs')
works quite well, backspace key seems to be OK.