Hi Jane,
It's difficult to know if this is just the rapid decline that often follows a "plateau" period of time.
It would probably be wise to check his medicines as the doses may be too high since he's lost weight. His shuffling gait, the slowness in thought and answers, and even the disorientation may be just too much medicine. Perhaps there is a blood test to check medication levels. If he's past the violent stage, he may not need the medicines at all now, but that's tricky to test!!
The other two things that come to mind that need to be checked:
* He might have a urinary tract infection causing the incontinence. It could be that he's just at the stage of being incontinent. My mom was incontinent for the last 18 months of her life.
* His weight loss means you need to check if he's eating enough. At some point in the AD decline, folks lose the understanding of use of knife, fork, and spoon. They can eat finger foods, but will need someone to cut their meat and perhaps feed them, too. Someone in the family should pop in for a visit during mealtime and quietly watch to see how your FIL manages by himself or if he's getting the assistance he needs. Ask the staff what help he needs.
My mother also went through as stage when she worried that her mother didn't know where she was and sometimes cried to go home to her mother. This happened about 20 months before she died.
Hope there's a fixable reason for this troublesome decline.
((((hugs)))) Barbara