Wow, that's a lot of text WoZeR
Excuse me if I missed something, I'm kind of tired
1) setting my cvars to 0 worked fine for me, I respawn right after the death cam. You can disable the death cam in TF2 by setting spec_freeze_time to -1 (default is indeed 4). You're right that this is not exactly instant, but it's damn close.
2) If you mean that you can't have every player respawn exactly 10 seconds after they died, I know that, because TF2 uses respawn waves. I can't reproduce anything of what you're saying about the 6 added seconds, that's why I thought it was weird that you had it in your plugin.
3) I think the respawn time is only reset when one of those outputs are fired. I hooked them all and set my respawn times again when they fire, and I have yet to see that go wrong or hear a complaint.
I can see why your plugin would break with a TF2 update, because it uses offsets that might change between updates. Mine however doesn't use any of that, so I doubt mine would ever break.
Last but not least, that's a sexy wallpaper you have there. Do you know where I could find that in 1680x1050?