I would say that what you're describing is developmentally appropriate for a 6 year old--even a gifted one.
My 12 year old son still likes to check in with me when he's doing his math. It helps him know he's on the right track, it helps *me* know he's on the right track, and he can redo any problems he's gotten wrong without having seen the answer first.
As for saying things are too easy or too hard--I've found that it is very difficult to find "just right," whatever that is. I've had some success over the years with getting my son to tackle hard problems without giving up immediately (I think he's so used to understanding things in an intuitive flash that when he doesn't, he thinks whatever it is is "too hard"), but not as much as I would like. Usually I respond by telling him to first *think* about the problem for a minute, and you'd be amazed at how often that works. If it doesn't work, then I will ask him questions about the problem until he is able to finish it on his own.
I've found that if I want my son to work completely independently--particularly when he was younger--I had to consciously place him well below his challenge level.
