That's what I expected. It's a bit weird that they didn't consider her power in the lowest player count, but I guess Adrenaline is better with more players in general.
Yes, it definitely is.
Have you tried the bot? I wouldn't play without it in a 3p game any more. You shouldn't underestimate it, it adds a nice little layer of strategy and isn't that hard to handle.
I haven't played with the expansion yet, but I'd get on house ruling that character for 3 players, pronto.
Sure, you can try it. My guess is that you end up with an overpowered weapon.