Hi night --- sorry to see you abandon this one, even if temporarily --- this was really looking good.
Here's a suggestion on remaking that boolean'ed piece, though, if you decide to revisit it. It requires the Ortho Knife plugin (
http://supercoldmilk.com/ac3dplug/orthknife.html ).
1. Create a cylinder with capped ends. Delete the surfaces on the end that will stay "open". Perform a Surface -> Combine on the other end. The 3D screenshot is shown as 2-sided for clarity.
2. Push the verts on the top half up using the size handle. (front view shown)
3. Resize the length a little and draw a line that we'll use to cut through the geometry. (left view shown)
4. Perform an Orth Knife, setting the Line as the knife, and checking both "Select new vertices" and "Delete entire knife object". Select the cylinder and perform a "Slice Side (YZ)".
5. Perform a Vertex -> Slice Surface, and select + delete the unwanted half of the cylinder.
6. Select the vertices on the opened end and perform a Vertex -> Extrude edges. Resize the selection by holding down Ctrl while resizing to get a proportional sizing.
7. Select the vertices around the bottom edge and resize them downward.
8. Then resize them to the right. You now have a more subdivision-friendly piece of geometry.
You can see in the subdivision example in the last 3D screenshot where I left the cylindar cap as a big surface, you get some "striping" that moves in toward the center --- this is lessened by slicing the surfaces up into vertical quads, as shown in the next-to-last image. If I hadn't combined the original surfaces, we would have seen a star-shaped pattern at the center of the surface.
HTH
Dennis