I think if your colleague had a confirmed reservation and ticket on OpenSkies, he could have taken a hard stance that trying to cancel it within the 21 day window (which were the terms of the original ticket purchased I gather) was unacceptable and he'd be filing a complaint with the DOT and taking AA to (small claims) court for any fare difference due for booking with AF/DL, he might have gotten them to keep the OpenSkies booking or permit the AF/DL re-accommodation at no additional cost.
It does seem a bit of a gray area as far as the conditions of carriage go, because they don't guarantee a specific schedule and disclaim liability from failing to operate per the schedule. Though I don't know if any of that has actually been challenged or held up in court. If their negligence/incompetence (the 2+ week delay before rescinding the OpenSkies offer) caused you to have to buy a ticket on another carrier that was more expensive, perhaps they could be held liable.
If the hard line didn't work, I think the second choice should have been to route via LHR as suggested.
I don't think you'll have any luck claiming miles/EQMs if you don't fly AA. You can usually only claim "original routing credit" for irregular operations (i.e., same-day flight cancellation).
You can still file a complaint with the DOT Consumer Protection division. They sometimes can get results, believe it or not.