Pc, I have a set of E-Z out bolt extractors if Drewpy needs to use them. I have a shitty cordless drill that loves to run dead on me half way thru any drilling job put the bits are new and I do have a regular drill bit we can use to get it started.
It looks like maybe the other bolt might have been loose and this one broke from holding the weight of the whole exhaust. I see you take after Drewpy with the washing skills... Its not just for vanity, you really do find a lot of potental problems on the bike like loose shit when you wash it. It just helps you keep in tune with the fucker.
But ya, No damage and I have never seen a bike truely damaged from running an open exhaust. Shit most harley's out there have no back pressure what so ever.
And as for JB weld... I love the shit but I think the heat is going to be working against you on this one.
If you need to use the garage and tools just let me know!
(and Ya I do have a garden hose also... = )