Thirdly, the FO probably didn't abandon the aircraft because it was his leg going home, and he knew he'd do a better job of it than the Captain.
Don't think so. This Captain then decided that he'd take the last leg home as PF too. See page 3 of the final report:
The last flight of the PF for the Operator was the return leg to Stansted, which he also flew as PF. The PNF recalled that this was a normal flight which complied with the Operators Standard Operating Procedures (SOPs), including a Flaps 30 landing at Stansted.