I'm afraid making the textual keybings customizable is too much effort for me. For the rest many of them you can already do, for example:
b) Home, Shift+end
c) ctrl+c + ctrl+v
e) the insert tag button already does this
And if you really want to do powerful things with the keyboard, learn to use snippets:
https://manual.calibre-ebook.com/snippets.html