If a Dragonfire Adept has the Draconic template (LA+1) then uses Humanshape, does that affect his alternate forms in any way? Would that allow him to apply his template to his other forms, or perhaps have access to certain other forms with an equivalent LA?
No, humanoid shape is simply Change Shape to any humanoid form. It never references your native type anywhere in the invocation, so it doesn’t matter if you’re Dragon, Humanoid, or Ooze, you wind up a Humanoid after using it.
As for Change Shape’s effect...
Thus, you keep the Dragonblooded subtype from Draconic.
But you lose the claws.
So you keep the darkvision, low-light vision, the bonus on saves vs. magic sleep effects and paralysis, and the bonus on Intimidate and Spot.
And you keep the ability score bonuses.
Also, point of interest, Draconic creatures don’t change to Dragon type, they just get the Dragonblooded subtype. They’re not very dragon-y to begin with. And Draconic is a pretty poor choice for a dragonfire adept.