you are not crew then.
You should try getting a few hours sleep in the middle of the day when you have only been up a few hours anyway just because you have a night sector home. Even if you do get some rest you will find your body naturally wants to sleep in the middle of the night.
I am just back from a BOS JFK B2B with 3 night sectors and the longest break we got was on sector one of 55 mins and the shortest being 45 mins. I would get more breaks working in a call centre or Tescos.
As for getting the cabin secure we also really struggled and it has nothing to do with breaks as all cabin secures are 20 mins out on long haul flights. We tried doing it 30 mins out on the very last sector and you should of listened to the abuse from passengers that caused.