Sorry if this is a repeat- I don't have time right now to read your other responses to see.
For middle of the night soak throughs, to speed up the sheet changing process, double sheet the crib. So it's mattress, waterproof pad, sheet, waterproof pad, sheet. that way all you have to do is peel off the top wet layer and get your babe back to bed. This saved us lots of frustration in the middle of the night.
When my son was soaking through at night we tried bigger diapers, two diapers and then found some success with a size bigger overnight diaper (Huggies is the only brand of those I think). We also found that it wasn't always a leak through but a leak out so keeping the diaper snug against him helped. Using a onesie to do this, a snug onesie, eliminated some of the problems I think.
Another suggestion someone had that I never tried was putting a cloth diaper insert into the diaper. I've never seen these but I'm assuming they're really absorbant pieces of cotton that just lie in a diaper.
I hope you get some restful nights soon!
J.