I notice you have not posted anything to the CROWELL or CROWE forums. These are among the best-documented surnames in all of North America.
Just bring up the front page of the CROWELL forum and pop YELVERTON into the 'key word' box at the upper left of that page, then click GO. There should be 100's of messages containing Yelverton that pop up. I suggest going back to the original messages (probably from 1997) and just read through the strings of mesages and replies.
After about 30 minutes, you should be much more enlightened about your Elishua and John Crowell. Take note of some of the problems and confusing information that the CROWELL/CROWE people are still trying to figure out.
Some branches of the Yelverton Crowell lines later came to Nova Scotia where I live, and there are 1000's of their descendants here.