How can I deal with undiagnosed, unrecognized, likely dementia?

Living as roommates with a very good friend who demonstrates behaviors not normal in aging. These have been confirmed by my own counselors when described to them by me. My friend recognizes nothing of these changes. So far none are severe enough to warrant a confrontation. Diplomatic remarks about my concern for him (without being specific), and mentioning specific memory lapses have been ignored. Neither of us have any family support. He is estranged from both his sons. While I do see counselors for help managing my lifelong Clinical Depression ( aka Major Depressive Disorder), which is successful, and they have suggested bringing in a social Worker who could help my friend, there’s no way I can suggest it to him as he sees nothing wrong.
I feel like I’m on tenterhooks, waiting for further symptoms to develop, while dreading the same.
After retiring from being a Home Support Aide because I no longer wanted to do this job, I do NOT want to be a caregiver for my friends. Yet how can I abandon him? I’m finding it very difficult to go along “one day at a time”, not knowing where I’m going. And it becomes more stressful as I become responsible for more daily aspects of life that he forgets or can’t reason through.
I’m an information/knowledge person. It feels like, in spite of all the information and knowledge I have, I’m in limbo. I hate limbo.
Any suggestions from anyone who’s recognized early onset dementia or MCI without a diagnosis would be appreciated.
PS. This is my first time on this forum.