Hello and welcome to HealingWell and the Depression Forum.
I would have to agree with you, your Father may need further evaluation for his dizzy spells and falling. This, to the best of my knowledge, is not a normal reaction to weaning off of Valium. I would not hesitate to make an appointment with perhaps a neurologist for your Father. I assume he has an oncologist? With his history I would look at his current disease to be sure he has not developed a new problem with his cancer dx.
I commend you on advocating for your Father and you are obviously a very caring person.
Take care and do keep talking with us.
Moderator: Osteoarthritis & GERD/Heartburn
Co-Moderator: Anxiety/Panic, & Depression
*~* http://www.healingwell.com/donate *~*
"When you find peace within yourself, you become the kind of person who can live at peace with others."
Not a mental health professional of any kind