Age Modifiers come based on your levels beyond the base racial hit dice. So Vadim, for example, is still a wyrmling dragon as he olnly has 1 level beyond base, which isn;t enough to progress, which Golgarthan is a very young dragon as he has three levels beyond base.
I know what devils are like, indeed I chose them specifically because they would be lawful enough to put something of this scale together and evil enough to go through with it. It's not a question of what they would do, it's a question of how dark you guys want the campaign to be. If you find yourselves in a position where the reasonable thing for them to do would be surgically remove your wings or torture you half to death, do you want me to avoid that, or just go straight ahead? It might not even come up, depending on how things play out, but I figure I should ask such questions ahead of time.
You get racial mods once, plus your mods for growing in age category and your usual +1 for every 4 levels.
You get 4 feats at 8th level.