I agree completely with your analysis but would like to add this to your observations.
On 3/9/2019, Boris sacked 21 of his backbenchers for voting for legislating against a no deal. This meant that he at that time ended up with a minority of minus 40. It did not make sense at the time but with hindsight it is clear that what he was doing was clearing out the old guard and selecting his own yes men and women. Most of these rebels either lost their seats, such as Dominic Grieve, or retired from parliament.
His calling an election then was also a sign of confidence that he knew he would win. He continually taunted the opposition until they agreed. These two facts to my mind, indicate that he was confident of winning.
Unfortunately I do not do social media.