I think Parkinson's can manifest itself in many ways . It's a bit like diabetes in that some things are very individual.
For example my mother was finally diagnosed quite late on, after the condition had progressed. Another condition masked some of the symptoms and her GP dismissed my concerns as unfounded. As a result my experience of having a close relative with it will probably be very different to yours. (and it is hard to 'talk'/write about)
You worry that he doesn't seem to want to know about you and your problems. I wonder if it's more a matter of not being able to express it so well.
I wonder if that is the case, certainly it seemed that way with my mother yet there were times when I realised that she did still care and worry about me; just as she had always done.
We get a lot of the clues as to how someone feels by facial expression and body language and we respond accordingly. These signals can be affected or diminished in people with Parkinson's . I found these changes to be very gradual and perhaps not noticed so much by my father because of this. They were more evident to me because I would go a couple of months without seeing her. I think that it must result in frustration on both sides.
My mum didn't really become aggressive but she certainly became very anxious and her response to this was panic.
There is always the problem of whether the drugs are working well at the time or not (on/off) and some of them do have various side effects.
I found the Parkinson's UK site very helpful in explaining things. There are lots of leaflets (though I've just checked their site and they have reorganised it and they aren't so easy to find now)
They provide a lot of advice and support for carers which I think is really important.
http://www.parkinsons.org.uk/content/ca ... parkinsons