I think its too strong.

Its straight up better than the dragon stuff straight up dragon sorcerers get, and they ARE part dragon.

Its also better than the dragon stuff dragonborn get. And they ARE part dragon.

Its better than both combined even.

My feedback:

I would use the breath weapon the dragonborn get, copied word for word including the set area based on dragon type and rest recharge.

I would copy the natural AC of dragon sorcerers.

I would change the game breaking dragon polymorph to the dragon wings ability of the sorcerer.