How to? Deinstalling TC/reinstating execution of bat files by cmd in Win7

By default, cmd starts with assumed /K switch. However, if you invoke a bat file through self-referencing association, Windows do some magic and actually call cmd with /C switch.

However, you changed this behavior by using "Open with…" menu on .bat files at some point.
This is what get saved as "Explorer\FileExts\.<ext>\UserChoice"
 
To finalise this topic - I don't know if far.bat works in TCC, but (once renamed to far.btm) it now runs OK with TCMD.

Thanks to all