use more sauce!
i learnt how to cook Lasagne in Italy and there they don't have it smothered in sauce like the english do. My ex mum in law told me that you should be able to cut a piece and hold it in your hand, like a piece of cake, without any sauce dripping through.
Sounds to me like you are making the perfect lasagne!
But I wouldn't pre-cook the sheets, if anything they tend to be stickier. I would just make tons of tomato/white sauce and put plenty in, making sure that all the sheets are covered before starting your next layer.
If you make too much sauce you can always freeze it.
x