How to split curved solid into two parts
Here is the way to do it:
1 Create a surface fill using the 3d sketch as patch boundary. Uncheck optimize surface.
2. Do a split using the surface as trim tool. Check all bodies and press cut bodies. Check the first body on the list bellow an double click on "none". A window will open for you to save a derived part from the first body. Then check the second body and save a second part.