How do GHA of vernal equinox, GHA of astronomical object and RA relate?
I'm using the Explanatory Supplement to the Astronomical Almanac 3rd ed. as a reference. The glossary tells us that Greenwich Apparent Sidereal Time (GAST) is the GHA of the true equinox of date, that is, "GHA(v. equinox)" in your equation. On page 80 equation 3.14 states

local hour angle = local apparent sidereal time - apparent right ascension (3.14)

If one is located on the Greenwich meridian, then that equation becomes

GHA = GAST - apparent right ascension (3.14a)

solving for apparent RA,

apparent RA = GAST - GHA (3.14b)

Comparing your equation

( GHA(object) - GHA(v. equinox) ) mod 24h = RA (object)

So your sign seems to be inverted.

Looking up values using UT1 and the Multiyear Computer Interactive Almanac, rounding to nearest second,

apparent RA 23 h 16 m 38 s
GAST         6 h 40 m 29 s

Substituting into eq. 3.14a, GHA = 7 h 23 m 51 s