Welcome to TP, Henry.
I do understand how you feel. My late husband was in a care home for the last three years of his life, and I know I felt guilty if I missed a day visiting him. And that was on top of the guilt that I was no longer able to care for him at home. I'm afraid it goes with the territory.
On the other hand, you have to care for yourself as well, Henry. You need to get out and about, meet people, and try to make a life for yourself. Not easy I know.
You could try U3A for a start. It was a life-saver for me, and is still a large part of my social life. And if you feel you could cope with a holiday, then go for it, either with family or friends, or with a company that caters for people travelling on their own.
As for your question re diagnosis, yes, there is a difference in treatment, as Alzheimer medication is not normally prescribed for people with vascular dementia. Having said that, my husband had a form of VD, was initially wrongly diagnosed as AD and prescribed the medication, and did very well on it.
These confusing diagnoses are I'm afraid quite common, even a scan may not be sufficient for an accurate diagnosis. The society has some excellent factsheets, which you can access from 'Alzheimer's Society resources' at the top of the page.
Please stay with us, you'll find the forum very supportive.