hi Jim, its not fully understandable where you want the fillet, i use metrics and its a little of a fiddle to follow your exact wish of dimension and i am a bit lazy today, maybe indicate it with points and describe it in the file or use the file i reworked and see if it works for you now.
if you explode the surfaces and hide the propeller shaft surface however its called then you have split edges you can also see that here on my image not so well if you use the command show edges then little black dots appear. run MergeAllEdges on this.
after that i dupped the edges shown below joined them and used fitcrv with the same degree and a tight tolerance to create 2 single cuves to loft a single surface. see if that helps, you still have a mess in the surfaces, i know you work with numbers from a table or something but i again advice you to try understanding what the surface is for and trying to recreate them as simple as possible. attached the file see if it works now better.
edit: some random testfillet with 0 on the front as you wanted worked now, some rest peaces where created which where not needed it joined automatically to a polysurface so i guess it should work from here on.
Problem Fillet.3dm (3.5 MB)