I think, that maybe you may have to drop the cat nap in the afternoon,
My DD is 9 months and has been having 2 sleeps for about 2 months. she has one around 9-9:30till 11-11.30 then one around 2 till 4, and then goes to bed around 6:30-7:30pm.
She does not sleep through so I can not help you with that.