To address the leak issue - I do have some diapers that I don't put on him when we are coverless at home, because they are prone to leakage. These I use under a cover when we go out. At home, I use thick fitteds that fit him well around the legs. I've never had a problem with anything leaking out, except for the inevitable dampness in front (sometimes).
I put a cover on him the other night when we went out to dinner, and when we got home I took it off and it was really hot and steamy in there.
It had to have been uncomfortable. It was a PUL, so wool might have been better but in this heat, I think the fewer layers the better.