Dear John,
That Council discussed the reunion of East and West, as we know. Among those present was the Met of Kyiv, St Peter Akerovych that Fr. Holweck in his "Dictionary of Saints" and also Patriarch Joseph Slipyj both say left that Council in communion with Rome. I don't know, I wasn't there . . .
St John Suchavsky was a merchant but well-versed in theology. He was asked by his Metropolitan to attend that council either as an informed observer or in some other capacity.
As he was travelling homewards, he landed in Beograde in Yugoslavia where a Christian merchant, jealous of his business success, reported to the Muslim authorities that John had cursed the Prophet etc.
John was tortured for four days. He was the victim of the "phalanga" where the soles of the feet are beaten with sticks until blood spurts from the toes etc. (I hope you aren't having lunch as you read this . . .).
In the end, he was beheaded as he refused to renounce Christ.
His cult is most popular in Moldavia and Bukovina where he is patron of the latter.
Alex