From your file a possible process lightly different than Phiro

Copy Past Move all general curves

For each curves : select each sides' path : Join each for don't have curves trimed!
Press Tab write Rebuild (hidden function) - choice in the popup 10 "Points" as you want...
...for have same number of points by curve

Loft curves by Curve (Circle...Circle), (Circle ..Curve) Side by side...Profil "closed"
Rounding is made by the final Loft function so no regulates possible but all depends of what do you want! :)





Last Loft with all curves selected!




Have happy new year! :)
(you can click on the ring for a little effect)