Re: sleep diaper??
I used heiny sherpa fitteds and they didn't live up to expectations and my LO was soaked by the morning as were his sleepers.
I went to diaperpin to see the best rated ones and ended up getting the Kissaluv fleece fitteds with their soaker/inserts for night time only, my LO is 20 months old and a heavy wetter and sleeps on his front some nights too.
I use the bummi whisper pants (also highly rated on diaperpin) as they have always lived up to expectations, and no leaks.
My LO lasts 12 hrs a night in these, no leaks, and I fold the insert in half and place it at the front where he pees and it works fantastically.