The prequisites for the Draconic Bloodline are using the variable BloodlineProgressionLVL however this variable is not being advanced by the Dragon Discple Prestige Class.
This means that Draconic resistances, breath weapon, wings etc. are not advancing correctly.
Line 2048: add the following to the bonus var section
Looks like the Robe of arcane heritage needs to be updated too to add 4 to the BloodlineProgressionLVL in addition to the BloodlineLVL.