Please post a screenshot of the mini-menu under Xfce. Please post your bugs on the new website.
WM_CLASS property is missing
add EWMH support for _NET_WM_PID to 3.8.8
Several focus bugs have been fixed in the icewm from https://github.com/bbidulock/icewm/
This may be a very old bug. Did you try a recent icewm? Also post the output of running xprop on the black window.
You didn't mention which distribution you are using. Apparently the HTML documentation for icewm is either missing or located somewhere else on your system. Does "locate icewm.html" work for you? If not then install locate and run updatedb.
This has been implemented in https://github.com/bbidulock/icewm/ where you can mouse wheel over tasks and workspaces if the mouse is over the taskbar.
Consider https://github.com/bbidulock/icewm/issues