Hello:
I am a LBD with Parkinsonism patient. Like your husband I was diagnosed when young.
Much of what you are describing can be indicative active of several things - like LBD/Parkinson’s or Parkinsonism.
Some of the issues - writing, voice, loss of ability to do things very familiar, not finding words or being slow to find them are common to both LBD and Parkinsonism (at least from “in here”).
IF there is a cognitive piece - both LBD and Parkinson’s Disease Dementia (PDD) can present very similarly.
Has a neurologist done any testing for Parkinson’s? A I mentioned I have Parkinsonism along with LBD. This is common and the symptoms of Parkinson's are there along with the other fun stuff.
Has any neuro-cognitive testing been done? That would creat a baseline to determine if ther is mild cognitive impairment (MCI) and be there to measure any further declines over time. I have them one once a year.
Finding a good team isn’t easy.
Have you looked at
http://Www.LBDA.org
They have a lot of great info about the disease, involvement with Parkinsonism, caregiver resources, and a lot more!!

I’m glad to help answer questions from a patient’s point of view.
I like to call it “from in here”.

Peace
Larry H.