Concerning Horizon Googles, according to Complete Mage p.133, it affects projectile weapons and thrown weapons only :
These lenses greatly increase your prowess with ranged
attacks, allowing you to accurately strike targets much farther
away than normal.
Description: These goggles feature small oval lenses in
a wire-thin frame. When worn, they are difficult (Spot DC
15) for others to notice.
The world seems particularly clear and three-dimensional
when viewed through the goggles, which glow faintly any
time you nock a bow or otherwise prepare to use a ranged
Activation: Horizon goggles are active as long as they are
worn; they require no special action to activate.
Effect: Horizon goggles grant you the benefits of the Far
Shot feat (increases range increment of projectile weapons
by 50%, and of thrown weapons by 100%).
According to the definition of Dissolving Spittle, it's a ranged touch attack i.e. a completely distinct thing:
Saving Throw: None
Incarnum forms a metallic blue-green torc around your neck.
The ends of the torc resemble black or copper dragons facing each
other in front of your throat. A constant bitter taste fl oods your
mouth, but it seems to make the fl avor of certain foods more
enjoyable—particularly well-cooked meat.
The infamous incarnate Murthien the Soul-Render, for all
his forays into the abomination that is necrocarnum, also
used dissolving spittle almost as a calling card. While this
meld is favored by chaotic and evil incarnates because of acid’s
association with both suffering and dissolution, incarnates of all alignments fi nd acidic spittle a useful weapon against
a variety of opponents.
As a standard action, you can spit a glob of acid at a target
within 30 feet. This requires a ranged touch attack to hit
and deals 1d6 points of acid damage. Using dissolving spittle
provokes attacks of opportunity.
Essentia: Every point of essentia you invest in your dissolving
spittle increases the damage dealt by 1d6 points.
So it don't.
Concerning the Rod, it says, when referring to enlarge :
ENLARGE SPELL [METAMAGIC]
Benefit: You can alter a spell with a range of close, medium, or long to increase its range by 100%. An enlarged spell with a range of close now has a range of 50 ft. + 5 ft./level, while medium-range spells have a range of 200 ft. + 20 ft./level and long-range spells have a range of 800 ft. + 80 ft./level. An enlarged spell uses up a spell slot one level higher than the spell’s actual level.
Spells whose ranges are not defined by distance, as well as spells whose ranges are not close, medium, or long, do not have increased ranges.
Since soulmelds :
Soulmelds interact with spells and spells interact with soulmelds in the same way that a spell or a normal spell-like ability interacts with another spell or spell-like ability," and, "Spells, spell-like abilities, and magic items that could potentially affect soulmelds do affect soulmelds.
I think it would work, RAW.
I would not allow him to have an item which is less expensive than the rod of enlarge, out of balance : you need to compare items of equal power and their price should be comparable. If not, why would that item be created or bought? They become useless.
IF it doesn't make him stronger than a comparable class, it should be acceptable. Most spellcasting class can many good spells at long range...