Kai, the Unix way to Copy and Paste is far less of a pain than you seem to think it is. To wit:
- If you need to highlight with the mouse, doesn't it make sense to also do the paste action with the same device? Also, if you need to chord your buttons, you need to buy a mouse made this millenium. I can't think of the last time I saw a mouse for sale that didn't have a wheel (and hence a middle button as well). Sure, in some GUI apps you might be able to highlight with your keyboard, but that's by no means universal -- and when it comes down to it, highlighting is probably one of the few things that's more efficient with a mouse than without.
- God invented "focus to pointer" to solve this exact problem. Clicking to focus is such a pain.
- Firefox is just generally broken. Best to learn to live with it -- you'll live longer (see: "How I learnt to stop hating Firefox and solved my persistent chest pains").
- It sounds like your vim autoindenting is getting in the way, or your copy source is broken. Copying should preserve indent characters (spaces and/or tabs) correctly, if the source provides that information, and pasting is basically implemented in xterms as "typing" the contents of the clipboard.
- Shift+insert should take one hand, unless you're on a keyboard layout I've never seen before, or if Ctrl+V also takes two hands. All of the modifier keys are duplicated for this reason (or rather, the opposite reason).