You must have a boundary edge between a planar face and a cylindrical face.
If you don't want to see these boundaries - then set to Shaded rather than Shaded with edges.
On 2D drawing - set to hide Tangent Edges.
You normally add Feature Fillets rather than Sketch Fillets.
Can you ask your instructor to joint this discussion?
Part1c-Rev1.SLDPRT.zip 128.2 KB
The large hole in the bottom is causing the cuts in the tabs. I made that 3.375 hole a separate Cut extrude. The radius J Mather described is also an added feature. Maybe you tried to so too many things in one step.