Muhammad or Mudhammam?

Bukhari: Volume 4, Book 56, Number 733:
Narrated Abu Huraira:
Allah's Apostle said, "Doesn't it astonish you how Allah protects me from the Quraish's abusing and cursing? They abuse Mudhammam and curse Mudhammam while I am Muhammad (and not Mudhammam)"

The Makkans made fun of the Prophet (PBUH) by twisting his name because of its meaning being “The one deserving of praise” , and calling him Mudhammam (belittled one).

1) Why did Mohammad need to change his name to Mohammad?
a) Does this mean that his name was really not Mohammad?
i) His real name was Abu al Qasim (Tabari VI:102)
b) Why would Mohammad need to change his name?
c) Is it because Mohammad wanted others to see him as one deserving of praise?
d) Did Mohammad deserve praise for his medical cures?
http://muslimhadith.blogspot.com/2008/09/dr-mohammad-part-iv-case-of-lying.html
http://muslimhadith.blogspot.com/2008/08/dr-mohammad-part-iii.html
http://muslimhadith.blogspot.com/2008/07/dr-mohammad-part-ii.html
http://muslimhadith.blogspot.com/2008/07/dr-mohammad.html
e) Did Mohammad deserve praise for getting divine revelations (aka Quran Surahs) for sleeping with his child bride Aisha?
http://muslimhadith.blogspot.com/2008/04/mohammed-would-get-divine-inspiration.html
f) Or for his sound business advice?
http://muslimhadith.blogspot.com/2008/05/when-you-bargain-say-no-cheating.html

2) Or are these the same reasons why Meccans would call Mohammad "Mudhammam"
a) After all, even the black man Nabtal would make fun of Mohammad so much that he would call him "all ears" to which Gabriel came to Muhammad and said, 'If a black man comes to you, his heart is more gross than a donkey's.'
http://muslimhadith.blogspot.com/2008/08/satan-looks-like-nabtal-sturdy-black.html

3) Why would Bukhari include this verse?
a) Was it to show that the most abuse Mohammad ever received was name calling, and as mentioned in several places, the worst that ever happened to Muhammad is an episode in which Abu Jahl and others mocked him while he was praying by putting the intestines of an animal on his back (Bukhari 4:241)? The men who did this were later killed by the Muslims.
b) Was it to show that the Meccans never believed Mohammad when he lived in Mecca because he was being nonsensical (i.e. prescribing camel urine, receiving divine revelations while having sex with his child bride)?
c) Was it to show that Mohammad was actually the butt of jokes in Makka, and not the esteemed person who he thought he was by giving himself the name "Mohammad"?