I've been dairy free for over 4 years now... it's not that hard... but I would say that if he has a problem with dairy than he probably also has a problem with soy... so I would go with almond, coconut or rice milks for substitutes... I haven't found a fake cheese that I like so I totally gave that up... other than sometimes I'll have it if we're out and then I totally regret it later... I use coconut oil as a butter substitute... and really it's pretty easy and I feel a ton better when I'm good... and feel like crap if I have any, so it makes it even easier to be dairy free LOL
hope he feels better... and yes, it made breastfeeding better and my boys much happier... my boobs weren't as engorged and my boys where happy and thrived and no reflux pain
and that's how I found out that I too had issues with dairy when I was feeling a million times better and no more sinus issues and congestion and why I'm still dairy free and plan on being dairy free for the rest of my life