Now make a circle (spline) (place it exactly in the same possition as the rim, using the allign tool) then go back to the mesh and just extrude the faces to make it look like pic7.

pic7

Delete the selected faces and go to vertex mode. now weld the vertices so you get no holes in the mesh. as shown in pic8

pic8

Select all the vertices you just welded,  and scale then all together so they fit inside the spline-circle, and you might have to rotare the selected vertices in pic9 so all outer faces have about the same size.

pic9