How long since you got the original piece? Without that information, it's hard to tell if it's too dark.
As far as comparing a drawing to what goes on your skin, you can't. It's dark, but too dark? Depends on how long you've had it.
As far as going over budget - didn't he give you an estimate? If he said he'd be 4 hours and took 10, then you've got a legitimate complaint. If you didn't ask how many hours the piece would take, that's on you. Some tattooers are just slow.
You said, "I found a shop that does alot of what I like." Well, a SHOP doesn't tattoo you. Did you look at the specific person doing the tattoos before you committed? I mean did you look at ALL of his work that he has posted? If not, you should have. If you did, does yours look darker that what you saw?
It sounds like you and the artist didn't do a very good job of communicating.
4-6 weeks to heal. I'd let it heal before you do anything else.
