Hi,
Most probably your father in law is experiencing the symptoms of
depression. Please keep in mind that mental disorder (particularly depression) are often associated with
diabetes.
In addition, age is also a factor in contributing to senile disorders (mental changes due to age).
Therefore, I could suggest to let one person look after him, never let him alone. Try to slowly suggest to your father-in-law the normal activities explaining that sleeping is not good to overcome his current problems.
However, I would suggest to be as patient as possible to avoid further problems.
With regards to his hiccups, to my opinion, it might also be related to problems with the
central nervous system (this is also supported by
thorazine prescribed by his doctor). However, I would suggest to talk to his doctor to exclude other problems related to stomach or intestinal tract.
At last, be patient. Diabetics, especially, aged-people are more difficult to treat when mental disorders appear. Try to be as close to your father in law to help him with patience.
Hope it helped!