[PF] Faerie Dragon Cohort Help

[Periaden]

Background:
    My DM is planning to revive his Jade Regent Path game, it was shelved before the third book, I had joined this gaming group as he ended it, but now there is interest in restarting it, I am making a 7th level Drow Conjurer with the Teleportation subschool (cuz: Shift is awesome). The rest of the party is a Hunter (unknown race), Half-Orc Warblade, and a 3.5 Scout (unknown race).

I have my character all planned out, however the difficulty lies in with my Faerie dragon friend. I had originally planned to take improved familiar and gain him that way, but with my rp background and how I acquired him, my DM was open to suggestion (it was mostly his idea, I believe) that I could instead take leadership and still have him follow me.

Now, I am ridiculously attached to this dragon despite I haven't played yet. My difficultly lies in advancing him as a sorcerer. I have little experience doing so with monsters with PC levels. The Faerie Dragon counts as a third level sorcerer, in addition to his three levels of dragon HD. So how do I make him a fifth level character, as leadership grants? Also, I can't for the life of me figure out his skills modifiers.

I plan for the Faerie Dragon to compliment my spellcasting, as I am concentrating on mostly summons, misdirection/illusion and utility. The Faerie Dragon starts out with greater invisibility as a spell like ability 3/day. Has grease, silent image and sleep for 1st level spells, and dancing lights, flare, ghost sound, open/close and mage hand for 0 level spells.

Any suggestions or tips for how to do this is highly appreciated.

[linklord231]

Disclosure:  I'm not an expert on Pathfinder, so this may be wrong.

I think in PF you're supposed to treat CR as ECL, and then advance via class levels.  So to make a CR 5 Faerie Dragon, you'd start with the standard CR 2 creature and add Sorcerer levels until you hit CR 5.  According to the rules here, each Sorcerer level would increase his CR by 1, and the spellcasting would stack with his racial spellcasting.  Additionally, he'd get +4, +4, +2, +2, +0, and –2 adjustments to his  ability scores, assigned in a manner that enhances his class abilities.  Obviously you'd also increase his hit points, skill points, and so on as usual.  I think the save DC on his breath weapon would also increase because of the additional hit dice. 

[Periaden]

Most of that I have understood. My confusion stems from the stacking of sorcerer levels. He counts as a third level sorcerer, but the CR is a 2. So, do I add two levels of sorcerer or three? Would he gain the bloodline abilities as a fifth level, or would he only gain the abilities from the actual levels if they were two or three levels? If he only gains two levels of sorcerer so that means he gets the BAB, CMB, etc of a second level but the spells of a fifth?