Hi Sun, so Transform > Array > Circular with 24 items should work to replicate those surfaces into the pattern you want - it's easier to replicate the surfaces that way than to have a whole lot of separate curves created that you then need to loft in pairs.

So then take your main uncut ring base object and select it and also select all the cutting surface objects too and run Construct > Boolean > Merge - that will maybe crunch away for a minute or two and slice up everything. Then you can select the main body piece you want to keep, and do a Select > Invert to flip the selection and delete all the little pieces. That's how I got the attached 3DM model version.

By the way, it's handy to put invert selection on a keyboard shortcut for I so you can just hit I to flip the selection, to do that go to Options > Shortcut keys and add in a new entry, put in I for the key and for the command part paste in the following:
script:moi.geometryDatabase.invertSelection();

So with this simplified surface structure it does seem to fillet much better, like this:


So the tricky part is that the surface intersection command produced some curves that were kind of a bit messy to be used directly for creating new surfaces off of since they were made up of several segments. I think that in the future I'm going to automatically run the results of the intersection through that Rebuild process but for now you'll need to run them through Rebuild as an extra manual step in order to get a more simple curve structure that will then create some more simple surface structure when you build with them.

Hope this helps!

- Michael