This site won't let me cut and past so the following paras.are numbered.
(2) I am wondering what side effects your dad is worried about. As far as I know, at his age the first line of treatment would be one of the levadopa formulations to replace the missing dopamine most likely Sinemet and/or another drug which enhances the availability of the dopamine you have still got (Rageline/Azilect)and I have not heard of particular side effects apart from some people not being able to tolerate particular formulations. The other main treatment involves dopamine agonists where there is a about one in five chance of developing compulsive behaviour . There is said to be a risk of the development of diskinesias (involuntary movements) with Sinemet and even this is disputed as some say its the natural development of the disease in some people any way.
(1) I am not in any way medically qualified but I am concerned because the main principle is to take sufficient medication to maintain function, i.e. aid you to "use it and not lose it" unnecessarily quickly.
(3 Meanwhile what are the risks of driving with the shakes assuming this is what you meant when you mentioned his hands. However, I assume your father has informed the DVLA in which case he will already be on a three year licence granted after referring to the Consultant . If you declare it on your car insurance they do not discriminate because they assume you will have satisfied the DVLA.