I wouldn't worry about the weight issue too much, I saw a guy yesturday out riding in lycra who had one of the biggest beer guts I'd ever seen! But the first thing I thought was "GOOD ON YA MATE! get out there and give it a go..."

Then I realised he was riding a really funking looking cannondale! DAMN! SUCH a nice bike!

Your hubby has to get out there and try the bikes that are right for him. Because of his size I'd even suggest trying all sorts of different saddles as well (just like we girls do)

AND because of his back a hybrid or a flat bar roadie might be the way to go. You'r in a comfortable upright position instead of a haunch.