I agree with his fourth point that discrepancies in the gospels do not argue Jesus never existed. Such discrepancies could be said about “most decent historical sources … such as contemporary biographies of modern figures” which would not prove they never existed. Husband and wife often disagree about their memories about things that happened years ago, months ago, weeks ago, days ago, or hours ago. Sometimes they both must be wrong; yet this misremembering is related to something that happened. It's faulty memory, not no memory.
An easy approach would be to look at the essence. Behind the details of all the branches of Science we see the essence: Science is the study of laws of nature (with a view to make use of them for our benefit) which means everything in the nature follows certain laws which would further imply that humans also must definitely follow certain laws that contribute to welfare of their own and of others if they want to enjoy their lives.
Similarly, behind the details all the branches of religion we see the essence: All great religious figures such as Buddha, Jesus, Mohammed …were sent by God to restore the remembrance of God which would help people to be good citizens of their respective countries. Hence what they spoke was truth beneficial for the people in their respective contexts. Later, commercial minded followers added things to the original teachings which make a mess of everything giving a reason for modern readers to doubt the historicity of religious leaders. (Mathew 13:24-30; Acts 20:29, 30) Thus what is of absolute clarity such as stated in Mathew 7:12, 21-23; 25:31-46 …are really from Jesus where as verses such as God-dishonoring (eg. John 9:1-3 …) are fabricated later.