Something's not making sense here. If it's not the starter (you replaced it) and it's not the battery (you replaced it) and it's not the clutch (you replaced it) then something's not doing what you think it's doing.
Did you adjust the free pedal play to accomodate the new clutch? There's not much difference in distance between a clutch that's engaged vs. one that's released. If you look at the action of the slave piston pushing the throw out bearing arm it's only about a half inch of movement. Anything less than that and it's not going to disengage the clutch fully. If the fluid was black that's a good sign the seals are worn. Look for signs of leaking at the dust boot of the master cylinder where it comes through the fire wall and at the slave. It doesn't take a lot of air or much of a leak to stop the hydraulic action. If some one in the cab pushes down the clutch to the floor and you can push the throw out bearing arm back you've got a seal leak and your clutch is not disengaging. A bad cable would probably sizzle rather than slow the start. The problem sounds mechanical.