I'd personally like to say that the example given is wrong...
It's the only example they give! What can you compare it to!?
EBT: Does the 1.5 modifier also increase the bonus damage done? If not, why not.
What bonus damage? The Strength bonus?
Of course not. The damage done is 1d6. Empowered, it's 1d6 x 1.5. It has a Str of 19, so you add 4 to that.
It's like an Empowered Shillelagh. It does 1d10 x 1.5 damage, and then you add the enhancement bonus and your own Str bonus. The +1 and the +Str in this case aren't random numeric effects, they're constants that modify the random effect.
For a Magic Missile, it's not 1d4 damage with a +1 modifier, it's 1d4+1 damage. There's a difference.
Does the 1.5 modifier also effect the +1 tentacle per caster level?
Same question goes for Mirror Image (+1 image per caster level), Cure Moderate Wounds (+1 hit point per caster level), and Slay Living (+1 damage per caster level on a failed save).
I'm inclined to say yes. However, I wouldn't let the bonus hit points of a CMoW go above 10, or the number of figments in a Mirror Image go above 8.
Dispel Magic: Does the 1.5 modifier also increase the bonus to the roll from caster level?
No. It's like the Shillelagh example above - you don't multiply your attack roll by 1.5. An attack roll or a Dispel Check is not a random numeric variable of the spell.
-Hyp.