Create two bodies (+ parts) from a curved body

Hello,

What am I trying to do?

I disassembled a headset and I am trying to model two parts, that once assembled form the following shape.

I made the following part:

(did not upload)

To which I make apply a split line:

(did not upload)

How can I create two bodies that get derived from that part?

I believe I have to go through surfaces first.

I also get confused with the split that appears on both sides. Is that ok to just use half of that (the inner curve one)?

I did an offset 0 + delete surface, but I don't feel that's right.

Once I have the two bodies, how can I create two parts from it?

Additional question: how would you do that thing?

Thanks!

SolidworksParts And Features