This x 100. It broke, and it broke there for a reason. JB Weld isn't going to cut it.

In fact given that it cracked around a factory weld/location/mounting point, it probably needs some reinforcement as well.

My vote (not wool though) is Ex Officio, i had to retire a few of my oldest pairs recently, but 10 years for a pair of underwear is pretty damn good. anti-microbial, easy to wash/dry, etc.