I think a transpack is about the same weight as a regular backpack, when there's nothing in it. It's made more or less of the same stuff: canvas or some other heavy cloth, a few zippers.
Yes, your skates will fit just fine in the ICE, and you'll even have room for other things in the skate compartments. I wear a 5.5 and used to wear a 6.5 and they fit, and I squeeze my water bottle in beside them.
A lot of the skaters at my rink, including yours truly, have the ICE. I've never seen an Expo.