Have just acquired a copy of The Viking of 6th Avenue, Moondog's posthumous biography, written and published in the United States. Will comment further as I read deeper into its pages. Here are a few things.

Charlie Baum, sadly, is on the right track. God rest Dick Greenhaus, who at this time is very recently deceased; Greenhaus posted to this obit thread that Moondog was a Juilliard graduate; Baum disbelieved it. One of the first things I did when the biography copy came out of the packet, was to turn to the index and look under Juilliard. Nothing there.
And believe me, if I go cover to cover in the Moondog biography and find something about Juilliard regardless of the index, you all will be the first to hear about it.

If I recall right from glancing at pages of the book:

how he got by, in New York? There was a resident hotel called something like "Ariosto." Moondog could afford to stay there, if nowhere else, and it was his home for years. When the hotel closed, he had to work out other arrangements.

He was in hospital (in Germany) when he died of heart failure. And that proved a blessing, in light of the chronic illness that was affecting the quality of his life.
Diabetes made his final years uncomfortable, when they were not worse than uncomfortable. Neuropathy set in. He needed a catheter. On one foot, there were two separate amputations, one toe at a time. Until the diabetes took its toll, Moondog had stoically endured all manner of privations, and his health had been robust.

Moondog's international travels made his resettlement in Germany possible; and Germany was not the only place to which he travelled. He was lionized in England, where Danny Thompson, bassist for the Pentangle, sometimes gave him a place to stay. Moondog would stay up at all hours, composing and working, and that meant he was using the Braille device, which was a little bit noisy; so much so, that Thompson initially guessed at an invasion of mice in the house. (from the book)

The biography includes a few pages of black and white copies of photographs; there is one of Moondog face-to-face with the then Queen of Sweden, another country to which he travelled.