This is only my two cents: No one can really tell you if its too hard or not until they play them. If your testers are telling you its too hard then take it down by 40% and try again. If its easy then take it up some place 1/2 way between. Rinse and repeat until you get it just right.

Balancing game play with difficulty is one of the HARDEST things to get right in game development and (from my companies studies) one of the main reasons games don't go. People either get board or they get annoied.

PS: As I stated before if you want to send me a copy I'll give it a go since their is no way in hell I'll get around to completing my entry (life is just too busy to complete, but I can squeeze in time to play).