Big nasty,
I would say just start over with a new breed. It's not working out and you'll waste more precious time and money trying to fix em with crosses. If you gotta cross its a failed project. Get a bulldog. No wanting for courage there and you be breeding them exactly for what they were intended, and use them the way they were intended. Pits true callin aint in the woods, and they like to fight hogs too. Cut your losses. You could end up breeding just to get your money back. Thats not gonna do anyone any good.
Forgot to add, if your running one style of dog for everything? You will need to have division of labor to use a bulldog. So you would need some good curs. I know of people who have some real nice ones you could hit the ground running with.