Hmmm I'd say the dream feed could be causing the wetting through.
You could include a nappy change for that feed. Change him first then feed him back to sleep. It wouldn't be a dream feed then though would it LOL!

Have you tried to go without the dream feed. He may not actually need it...

If you don't want to try that then you could give huggies a try. When I used sposies I would use the cheaper ones during the day and huggies at night with no leaks.