Carol - that was absolutely fantastic. All the praise above is well deserved. Just incredible.
As far as singing on key - if you can hear that it sounds off-key then you can practice to get it on key, as Knight46 said. I think it's another case of the so-called 'muscle memory' - your brain will tell your singing apparatus what to do, after you get it OK and do it enough times.
If you are someone who can't hear that it's off-key then that would be more difficult.
As far as singing, I think your voice can do well, it is real pleasant and 'round' (maybe that's timbre).
I'm really impressed with the whole thing. You go girl!
