1.) No, but you want to boil as much volume as you can possibly handle.
2.) Doing a split boil works fine, but it's not a good idea to boil extract that is too concentrated (i.e. not diluted with a sufficient amount of water). That'll result in darkening of the wort and melanoidin or even burned flavors that would be inappropriate for a pale ale
3.) DME should definitely be boiled to sanitize it.
The Fiesty(sic) Goat Brewery est. 2007 & Clusterfuggle Experimental Ales est. 2009
Planned: sLambic II, Flanders Red II
Primary: Fat Man Porter, Orange Blossom Mead, sLambic I
Secondary: Flanders Red I
Kegged: 3 different ciders, Janet's Brown, Barrel-aged Stout, Hallertau Blanc Pale Ale
Bottled: Flanders Red I