I believe the information shown for taskbar buttons comes from the executable information, so at most you could either recompile window_frame_host with your own labels or edit it using Resource Hacker. The earlier-mentioned third party rewrite was supposed to address the issue, but I’m not sure when that’s going to be out.
A black preview is a side effect of however Windows calculates them - I’m not sure if this is easily fixable.
If the game crashes or closes abruptly (without executing the normal game end events), there’ll be no one to tell the frame window to close, so it will only do so once some kind of interaction happens.
If your only desire is to have borderless fullscreen, OutsideTheBox is more reliable.