Cerebellar Ataxia can be idiopathic or hereditary, there are multiple types and within that type it can give you whatever symptoms it wants and progresses at whatever rate it wants.
Exercise (riding stationary bike, swimming, walking) seems to help. PT does seem to help you walk better but make sure they take care of neurological conditions not orthopedic. There is a difference. A physical therapist changed my life. They taught me to walk better so I don't trip which makes you more vulnerable to falling, taught me how to go up/down stairs, walk on uneven ground, go up/down ramps. If you need canes or anything else they will work with you with that. The right therapists are out to improve your life. It seems like a long time but I went for 6 months, 2 times a week. That was a few years ago. I haven't had to go back but I use what they taught me every time something comes up.
You are in the US so if you haven't applied for disability, do it. Just remember you can't collect any income while their decision is pending. Once you have been approved you can work some and make up to about $1000/month. Also after 22 months you are eligible for Medicare and that has Silversneakers which allows you to have memberships to places to work out (multiple places if you want).
Find a doctor that it willing to work with you. I just go to my primary care doctor and when he can't do something he refers me out to someone who can.
This website is a great place to just vent or to get advice on anything.
You'll probably have to do most of the research yourself. Unless you go to a doctor that specializes in ataxia very few doctors are going to be "up to speed". My primary doctor can check my balance just as well as a neurologist and he's cheaper. The only time I go to a neurologist is when I have a change in my symptoms and my primary doctor can't do anything.