Read the acknolwedgement you are being asked to sign. It does not require you to admit any wrongdoing, including the findings AS made and details in its letter. It simply acknowledges that you have read, understand and agree to the t&c. Nothing more.
That's because AS could care less whether you agree with its findings. It doesn't need that in order to suspend or terminate your account. Thus, it does not ask you to admit.
It's your choice. Sign and agree to the rules, including the specific restriction on miles use which goes beyond the ordinary AS terms, and enjoy some travel. Or, don't sign and move on.
As to the multiple itinerary issue, this is the product of improved software pioneered for AA., Inventory "spoilage" caused by impossible bookings is costly to air carriers, so they have spent money on stopping it. You may not book (for cash or award) tickets which could cannot possibly use.