"thickness is mandatory even in 2D model" This is not true, you have made a mistake somewhere.
Create a new Static Structural system in Workbench, RMB on the Geometry cell and select Properties. In the Properties window on the right side of Workbench, there is Analysis Type that defaults to 3D. Change that to 2D. NOTE: If you already built a model, you cannot go back and change 3D to 2D after the geometry was attached to the Model. You must start over.
Now start the Geometry Editor. Create the surfaces in the XY plane with the axis of rotation along the Y axis. These are surfaces, not 3D solids.
Double click on Model to start Mechanical. Click on Geometry. In the Details window, you can set the 2D Behavior to Axisymmetric. No thickness is required.
Please reply with confirmation that you have done all these steps.
On the substeps, you didn't say you set the minimum substeps. I don't care about the max substeps. And 45 substeps may not be enough, you might need 100 or more.
Please reply with a zoomed in view of the elements around the tip of the rod.