Welcome back to the darkroom.
You really can't tell much about a negative from a scan, but it doesn't look like you have overdeveloped. It does look possible you've underexposed. You may already know this, but judge your exposure from the important shadows, which should show significant tone above the clear edge. Judge your development time by the densest areas of the negatives (highlights in the scene). Only experience (or a densitometer, since you seem technically inclined) is going to really let you judge that. A scan won't unless you are way overdeveloped.
To me, a darkroom print is the best way to evaluate the negative. But if you are only scanning, you can benefit from slightly less development than is ideal for darkroom printing.
BTW, it seems like it would be a good idea to start with a standard developer like D-76 (or Ilford's ID11) or Xtol. D23 is fine. I used to use is a good bit, but it is not as good a general purpose developer as those others. Then you will have much better documentation.
If your climate allows to standardize developer temperature, that is better than chasing your tale needing several different times. I warm my developer to 70F in winter, and run at 75 in summer. A simple dish pan water bath works great.