Not my area of expertise, but this sounds like something for a qualified smith. That barrel is not just loose, you've got headspace problems. Bet the fired shells have putruding primers. Do NOT fire this weapon until it's been checked out.
When J B Browning designed the 93/97 guns, he built them to last and be adjustable to make them last. That 97 must have fired zillions of rounds to get loose like that.
I'm no gunsmith, but IMO, this is fixable. I did see some 97 bbl assemblies for sale in Shotgun News some years back, but I've no memeory of who had them or how much
