The Vaccuum/Gas stats are for vaccuum races with gas colonization tech.
While stock SE4 only starts you with that combination on High Tech settings, your mod does allow it as a starting setup, and Vaccuum races can always research it sometime during the game.
Don't hold up the test game.
I'm just saying that the speed racial traits are quite probably too cheap, and that the storage traits are much too expensive for the effect they give. (Taking a second colony tech gives you 4x more effect per point spent)
For the images, try only including the changed portraits in your mod. SE4 will look to the default folders (IE the regular imagemod) for the missing images.
You may also want to send your new images in to be included in the imagemod directly.
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The "agressiveness" and "defensiveness" traits are underpriced in stock, and are almost always maxxed out for competitive games.
You've made them even cheaper, so that it is possible to get +40% to attack and defense.
That means, at a distance of 5, a player with the maximum attack/defense stats will hit over 90% of the time against a plain player.
The plain player will hit back with only 10% accuracy.
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As for maintenance:
in settings.txt - "Empire Starting Percent Maint Cost := 25"
So, when you take engineers for a 10% bonus, you only pay only (25-10 = 15% of the build cost per turn)
Even if you take the politicians culture and +30 to maintenence reduction in the characteristics window:
25+10-30 = 5% of build cost per turn for maintenance.
For only 875 racial points.
Maintenance at this point can't go below 5% (hardcoded)
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What I suggest is you set:
"Empire Starting Percent Maint Cost := 100"
That way, it costs 1875 points to buy +50 maintenance reduction.
100 - 50 = half maintenance
In other words, this change makes +10% to maintenance reduction actually mean "10% cheaper ships", instead of 40% cheaper
Now, since as a side effect of the above, everything costs 4 times more in maintenance, you need to do the following:
In your ships, add:
Ability 3 Type := Modified Maintenance Cost
Ability 3 Descr :=
Ability 3 Val 1 := -75
This multiplies with the racial maintenance; 75% off here means 1/4 the price, negating the 4x side effect above.
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Alternatively, you could divide your culture maintenance modifiers by 4, quadruple the price of maintenance reduction, and reduce the "Characteristic Maintenance Aptitude Max Pct" to taste.