[Robe]

There has been a lot of confusion on this a/c range... the Washington Post Range Map is for a 777-200, MH370 was a 777-200ER (Extended Range) It has a range of over 7,000 miles.
British Airways operates a daily flight in a 200ER from Beijing to London. That's real close to the Longitude where 370 disappeared.
This airplane is in the Mideast somewhere

[FAA]

Fully fueled, yes. Common practice these days is to carry only what you need for the planned trip plus a small reserve for delays/diversions, etc.

Distance from KUL to PEK is 2700 or so miles.

Speculation on whether the airplane took extra fuel in KUL but the Malay authorities, presumably knowing this and researching it, still believe the airplane only had enough for the planned trip.