If I recall correctly, anyone who viewed the "About Me" section of his Patreon page will be able to find his email address so they can contact him.
As for your estimates, I sincerely hope you're right, but I'm not that optimistic. At most, I'd lean towards a 50/50.
Your outcomes for John are excellent, but I'd rather give him some serious psychological torture before send him to hell (for example, John being so obsessed with history and genealogy, he must care a lot about the legacy and the image he will leave behind when he is no longer there, so MC could torture him by saying that he will make sure that he is remembered only as the perverted businessman who abandoned his family to avoid jail (in reality MC would kill him but he would hide the body) and MC could better justify his relationship with Nicole in the eyes of others by visiting her often as a friend but then that "friendship" evolved into something stronger (something similar to those firefighters who left their wives to fall in love with the widows of their dead colleagues on 9/11), while the child she is expecting could be passed off as John's child simply so that he/she would inherit the real estate agency even though MC would later decide to "adopt" him/her to avoid that a connection with John could harm him/her in the future). Another alternative would be to give him the Clyde Shelton's sadistic treatment on an operating table.
However, I still think that in one of the possible multiple endings of the game there will be an ending that will end up with John but it will be totally bittersweet (perhaps a car accident was planned as a method to finish him off, but when it happens, he was not alone and his companion would also die).
