I've used modified Denon 103R's for the better part of 5-6 years now, the most recent versions being one in an ebony body that has been retipped (and potted, as Zu does with theirs) by Soundsmith with their $250 retip (ruby cantilever and line contact stylus) and currently a 103R in an aluminum body, also potted and retipped by Soundsmith with their midline $250 retip.
While I found the stock conical on the 103R to sound best right around 2.6 grams VTF, I can dial back the retipped versions I have to around 2.450 to 2.475 (yes, it will be that sensitive to VTF when it fully breaks in and you get into those zones). Going below that in terms of VTF the cartridge becomes very "airy" and detailed but loses the drive, slam and top to bottom coherency that the 103 series is really famous for and excels at with an improved body. Lower VTF may give you more "audiophile" qualities but will sound less like real music IMO. If I had to track mine below 2.45 I would probably look for another cartridge. Based on my experience, you are on the right track between 2.45 and 2.5 for VTF.
I would expect the paratrace to be very similar to Soundsmith's $350 retip. That would mean that it should be a detail champ but will also be extremely fussy on setup as you are finding out. But get it locked in and you will be rewarded.
FWIW, even Soundsmith's $250 line contact retip is a ton more sensitive to proper setup (alignment, azimuth, VTF/SRA) than the stock conical stylus on the 103 series.