You can't. You must earn them all again on Xbox Live, as well as the ranks, perks, weapons and emblems. Infnity Ward and Microsoft did not allow players to do this because players could cheat to aquire everything, which they do anyway by using hacked servers.
It is impossible to transfer anything that you've earned in spit screen mode to Xbox LIVE without modifying the game.
yes
You can play Special ops splitscreen you can also play splitscreen in multiplayer
yes
yes you do
There isn't one.
http://callofduty.wikia.com/wiki/Callsigns
Yes you lose everything but titles and emblems
By getting into a tenth prestige lobby.
Lots of people do by hacking very few probaly 2 or 3 actually have all titles
Because you have Xbox live and MW2 can be played online?
do some challenges they will unlock it for you ------------------------- Completing every challenge will unlock every title.