Without being too much of a dick about it....here's what I have to say:
It's a PROTH!.
These were always low end grinders...OK for grinding plates to loose tolerances and average finishes, but they were never intended to be anything else and their construction reveals that.
So my apologies for the dickish comment above, but you sadly cannot have super high expectations for this grinder, and routinely grinding to tenths with the dials alone is one of those expectations.
Having said that, I have used a Kent (and a Proth) at various times and they are very similar machines.
I owned a Kent for decades and I ground a lot of sophisticated tight tolerance stuff on it, in spite of its shortcomings, so all is not lost.
On my Kent the downfeed was identical to your Proth, and the way I'd kiss tenths, was to tap the downfeed handle with my index finger while watching the vernier scale and also smearing the job with Sharpie then dusting it off with the wheel.
I could pretend to reliably grind 2 tenths that way.
The Jones and Shipman I have now does have a half tenths graduation on the downfeed and I can mimic what I did routinely on the Kent with the J&S and the result is the same as close as I can measure...it's just that I need not screw around so much.
So a bit of technique will be needed to get you there, but it can be done.
Be sure the grinder is in good nick...it has to grind nice and flat, and the spindle needs to be good.
You can benefit from balancing your wheels properly and you can benefit from selecting and dressing your wheels properly.
Grind wet when you can, don't push the machine too hard (Proths have wimpy spindle housings and short downfeed ways as I recall so the head on the machine I ran in the early 1990's was floppy even when new.
We parked a lump of steel on the head to give it a bit more mass, except when slot grinding with it and we needed the spindle to be reasonably square to the table.
But it was mostly a plate grinder so the spindle weight rarely moved.
So despite my sniffy remarks, you can turn it into a perfectly usable grinder...just don't expect it to be as good as a hundred thousand dollar Okamoto.