Actually, the planned pair of cons would get medieval on the betta.
I'm going to have to recommend against dividing this tank per the plan in the OP. Dividing a 48" tank into thirds means that the cons would only get a 16x12 footprint. This really isn't enough. I know it works in terms of gallons, but vertical space means little to cons. They need a lot more horizontal space than that. The smallest recommended tank size for them (20 long) has a 30x12 footprint.
The betta is not compatible with the other fish you have listed. The kribs and/or swordtails will likely kill it, let alone the other fish you mentioned. I don't know much of anything about the knife fish, but I'd assume it's like others and will eat anything it can fit in its mouth (probably including a betta).