Porthos, there is that old quote (Tibetan? Chinese?), it's something like:
"A journey of a thousand miles begins with one step."
My friend often says that her head is "filled with fog", and sometimes she says it's in her body, too.
I don't know if that is the PD or the meds or both, but it is a real problem for her.
Anyway, you have the right attitude, determining to improve your situation, stick at it, Porthos.
Maybe try getting some magnetic coils and use PEMF (Pulsed ElectroMagnetic Fields) therapy.
You can get a 10Hz mp3 (and instructions) from diypemf.com
You need to buy a pair of magnetic coils for about $25, and you plug them into an mp3 player (or computer or laptop).
The 10Hz mp3 must be added to the mp3 player (or computer or laptop) and set to loop (or repeat ).
I've tried this for minor ailments, and it seems to work.
Oh, and Xi Gong/Chi Gong is a really good thing to do also.
Ganbatte! (Japanese: Keep at it!/Stick at it!/Do your best!)