Sorry, forgot to answer your first question. When I did some research on A320 encoders some years ago, I think I found some info where it said that a full turn is 24 ticks. Not sure if that is true or not, but for me it works very good. If I’m not mistaken, I also used the FBW A32NX simulator, made a full turn, and looked how many steps that was. As you know, “research” is half of the fun 
As mentioned earlier, I use an encoder without shaft. I used to buy a few from RS-Online, but there it is now obsolete. I luckily found them also on AlieExpress (see here), where I immediately purchased about 20 of them. If you want to google them, the type is EC12E2420301. On RS-Online you even can download a detailed model for Fusion 360.
I made my own rod - below the design in Fusion 360. I’m using a plastic tube of about 6mm diameter (I think I purchased about 5 x 1 meter of that on AlieExpress for about 10 € - good for more than 10 years!).
The D-shape on top is done with my desktop CNC machine. The biggest challenge there is positioning the rod to do the cut - trial and error, and patience… again.
The rod is glued with superglue on the encoder. I even made a positioning tool with my 3D-printer (same machine - as you know, Snapmaker can do 3D, CNC and laser) to make sure that the rod is perfectly vertical. The last thing you want is that the rod is not perfectly on axis (yep, all part of the “trial and error” process - been there, done that - and then thinking of “how can I improve it”).