Newbe Question about Radii/Fillet

I have a part I wish to draw. It looks like a rectangle 30" x 6" on the front plane but the upper and lower bars are radiused to 400" in
the top plane. I started the part but inserting a plane parallel but offset 6" to the top plane. I drew a radius and constrained it to origin and defined the cord of the radius to be 30". I copied the radius to the new plane I inserted. I then drew the vertical bars to connect the end points. I now have a rectangle with square corners when viewed parallel to the front plane but a single radiused line when viewed parallel to the top plane. I then drew a circle to represent the cross section and sweep the radius along the 3D path I created. I've gone back to the sketch and tried to fillet the corners of the sketch but am given an error reading "Cannot fillet curves that are not co-planar." After sweeping the curves, I've tried using the Solid fillet command and got an error reading " the radius of the fillet is too large to fit the surrounding geometry. It may be too large because it cannot fit within a tightly curving face near a selected edge or it would inappropriately eliminate an adjacent face. Try adjusting the input geometry and radius values or try using the "Face fillet" option." This is a 1/2" dia bar swept along the curve that I had intended to use a 2" radius in the corners when formed. Can someone point me to what I've overlooked to be able to fillet or radius this part?
R. Wink
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