In my experience it's really hard to run a flying circus at 1500 pts. I am by no means an expert at playing the flying circus, but there are many experienced daemons players that would tell you the same.
Unless you are set on running that list, I would switch to a hound rush type list or possibly a hound rush/screamerstar hybrid. I have been playing with the latter recently. For me, it's fun to play and is very capable of giving tau and eldar fits, which I like very much
If you are set on flying baddies, however, there is only on suggestion I might make: Heldrake. If you lose the hounds, one greater reward (probably from the portal prince), and two Horrors, you can ally
CSM with a barebones sorcerer, 10 cultists, and Heldrake. Lands you at 1500 on the nose.