Mine belts didn't look much better, I used a citrus cleaner with stiff brush & lots of hot water, for rust on the webbing I diluted some Lime Away, scrubbed but did not let it sit before rinsing. Plastic polish on the buckles but the chrome that was bad can't really be helped, maybe some sliver paint.
The crack can be filled w/vinyl repair, Kits avail. at Eastwood. Lots of patience.