well splitting the model is easy, looks like its a nurbs model, so select an isoparm where you want to split the model then go to edit nurbs>detach surface (i think, havent got maya up atm)

the way i would do it, most efficient i find when doing any textures is using a texture map that you create in photoshop

ok, just another observation, i think the reason its not a straight line, or even a texture map wont give you a straight line is because of the positioning of your isoparms, if you take a look at a side view you can see theyre wavey, you need to fix that fix by snapping and moving CVs