Good to hear it’s printing better for you
A speed of 50 should be fine. 100 seems to just bee too fast. Someone explained to me that the faster speed builds up back-pressure in the extruder, which can cause missed steps and an inaccurate calibration. You probably already know this, but reducing your e-steps by X% has the exact same effect as reducing your flow rate by that same percentage. I usually try to dial my e-steps in very close, and get my average diameter very close, then do any short-term fine tuning with the flow rate.
There are links on here somewhere to procedures for getting it even closer, but the slower speed usually gets you fairly close for most purposes. Here’s one such guide: Triffid Hunter’s Calibration Guide. (I did not bother with the calcualtions for x, y, and z steps. They seem very accurate as set with the machine. Since the machine also came with the e-steps fairly close from the factory, I did not go to the trouble of removing the hot end in his “E-steps - Measure” section. I just dialed it in using the slower speed with the hot end in place, as you have already done. His descriptions in the sections I skipped are interesting, however, if you want to understand better what is going on. Much of the “Z-height” section does not apply to a machine with auto-bed-leveling/bed-height like the Mini.) The real value in this guide for me was the description under “E-steps Fine Tuning”
Another very helpful thread: A Strategy for Obtaining Great Prints.