Find a support group for caregivers, and/or for Dementia care giving.
See a Nutritionist or be referred to one by his Doctor. Each case varies according to the individual patient's condition/needs.
Care-giving for a parent, with health problems, is like taking care of a child, or harder. Thus, it is very important to join a support group and take an active role in his Doctor appointments and understanding fully, his condition.
Dementia is also a safety issue... so you have to look at it that way as well. They can't take care of themselves totally. And they get forgetful.... long term or short term memory as well. So learn all you can, about the condition.... AND since it is linked to his Parkinsons as well.
You need professional guidance... a lay-person, cannot guess at it or their needs. My Father-in-law had Parkinsons... he was on medication, had the tremors etc. He needed help with BASIC hygiene as well and bathing and using the bathroom.
Can you get a home health aide to help? Does he have insurance for that? It will help if you can get that kind of help... and being that you are a Single parent, with a child of your own. Make sure, that your son is not lost in the shuffle... it can be hard on the child too... to understand all of this and the patients needs.
Since you are a Single Mom... can't your family ALL pitch in for costs? And for helping? You should not have to shoulder the costs of it all by yourself... this is THEIR Dad too.....
and it is huge undertaking.
My Dad was ill for a long time too, and I and my family were care-givers for him. It also entails taking them to the Doctor regularly for appointments and check-ups.. All of which requires you taking time off (from work) to take them to the Doctor etc.
And... if your Dad has dementia/Parkinsons... can he even be left at home by himself? That is another issue... and a safety issue as well. What if he turns on the stove... and forgets to turn it off? These are very real concerns, with an ill parent and/or dementia and Parkinsons.
They cannot be entirely responsible.... for themselves, or in a homes daily details. And they often need Supervision...
Join a support group... ask the Doctor for a Nutritionist... and ask your Family for any physical help or financial costs to ALL pitch in for the care of your Dad.
KNOW... that it will progress. His condition will worsen... and you will need help. Tell your family. Medical conditions like this do not go away. It is a condition... that requires daily upkeep and MONITORING of their condition.
If you cannot handle the care of your Dad... have a "Plan B." And maybe he may need to go back to a care home.
You NEED to discuss all of this with your family/siblings. THEY should also be coming to your home to help and just to visit him.
All the best
Susan