Thanks for sharing!
Except for the lack of any service by the FRA concierges (I guess they just went home at 5p.m. or whenever their shift ends) it sounds like AC handled the situation pretty well.
The Steigenberger Hotel is a very decent hotel indeed (I wouldn´t expect anything better from an airline and I am indeed impressed AC put up all pax there, usually only SEs and J pax get to stay at the better hotels) and the food provided sounds much better than the usual $7 breakfast voucher and $10 dinner voucher (which obviously never comes close to covering the cost)
Kudos to AC for handling this situation pretty well (particularly as most of the events seem to have been outside their control).^