Breaker Short Circuiting
Alright. You have a short in the circuit wiring which was probably caused by switching out the receptacles and switch. That means there is a good chance there is a nicked wire inside one of the boxes and it is making contact with either the ground, neutral or even another hot wire (highly unlikely since you don't have two breakers tripping). You need to examine your wires in the boxes for any burn marks or nicks. Since you are tripping with all of the devices removed, I would start where the circuit begins.

If that doesn't work you may need to get a continuity tester and begin to "ring out" your wiring to see if you can find which part of the circuit is shorting.

PS - I didn't ask if the devices were daisy chained or connected through the devices. If they are daisy chained you need to disconnect and separate the splices before you start testing. In short break it into small individual pieces and find the piece that doesn't work.

PSS If you do have to break apart the splices don't forget to mark or identify all of your conductors.

Good luck and stay safe.