Just installed stand alone manager and still have no buildings
Be sure you are installing the Stand-Alone Addon Manager AFTER ALL the sceneries are installed.
Having a similar issue with ORD too(buildings floating above jetways).
Buildings floating above jetways doesn't have anything to do with this (if, with "floating buildings" you mean the FSDT KORD buildings), it's not an Addon Manager problem and not an FSDT problem but, more likely, an altitude conflict caused by another AFCAD coming from another product (usually AI traffic packages), in this case, use the free FSX Airport Scanner to search for AFCAD duplicates and remove them.