Since I don't have Simp1.shx, Simplex is substituted for it when I open the drawing, so I don't know exactly what your condition is, and your special-character fractions don't come through [a screenshot would really show it best].
But that gap [or lack thereof] is pretty tight with the Simplex font, too, so maybe that part of the issue is comparable. But the gap becomes entirely acceptable-looking [to my eye] with simply a reduced obliquing angle in the text Style definition -- say, 10 degrees instead of your 22. Can you live with a "less-italic" look, or perhaps even not obliqued at all?
Or.... Is there anything so special about the Simp1 font that you can't just use a different one that doesn't come out this way? I would think there would have to be something mighty special about the look of that font, or that rather extreme obliquing angle used with it, to justify all that Exploding/retyping/loss-of-associativity.
Kent Cooper, AIA