I've done a bit in 172's, including the permitted 'aerobatic' manouevers, (wingovers) and spins.
The aircraft at the weight you're flying it is certified in the utility category, which means it is capable up to 4.4G.
There is a required 50% safety margin, I believe.
I've never heard of a 172 in-flight break-up. The type has a reputation for ruggedness (like most of the Cessna high-wing stable.)
Every time I've spun a 172 at forward CoG, it has to be held in to the spin. If full aft wheel and into spin rudder isn't maintained, or a bit of power maintained, it will simply fall out of the spin into a spiral dive. Recovery is utterly conventional. It's a lady.
Hope that helps.