1. As an evil character you don't have to kill everybody, by leveling up sneak you steal things, which gives negative karma and means you still have access to vendors and such.
2. You can join the slavers.
3. I think you also get negative karma for killing the ghouls.
4. Even if your evil you don't have to do evil things constantly, just enough to cancel out the good and keep you evil in terms of karma.
Personally I get the quest to DEFUSE the bomb the moment I get into Megaton, then I go to Burke and get the quest to DETONATE the bomb, because I talked to Simms first I can say simms promised me more money than Burke, and get more money. With the pulse detonator in your inventory you can wait on detonating the bomb until you are ready. I also suggest to the wasteland survival guide a bit, then talk Moira out of it because you get the http://fallout.wikia.com/wiki/Dream_Crusher
i took the dream crusher too early i missed out on the molerat obliterating stick from
bliviongate: and the thing that makes food sanitary to eat .... this play through but ive been geting ull goodkarma longest i was max evil was maybe hours untill i got fingers and sold them
(my regulator HQ keeps getting a tatcked by stuff i swear a sentry bot lives inside teh palce cuz every time im there theres a hostile sentry bot
all the regulator buddies are dead and the finger buyer went missing i found them outside the hut (she wont run too far away will she id hate to have to scour teh wasteland just to sell a couple fingers (like 57)