1. i think the normal cellshader from the wiki wont change the shadows with dynamic lights, it only uses the sunlight i think. but every model has its own self shadow with the toonshader, so you should use MDL Geometry to get the shadows on the objects. maybe its possible to rewrite the shader so models will be affected by dynamics light.

2. i know your graphic style and your textures. i actually think you dont need any cellshader. your style is perfect like it is, cause you drew all the details and light effects on the textures. it looks a bit like Kingdom Hearts. They dont use any light source either, they actually just bake the light onto the textures and draw the highlights and shadows.

3. your character has solid colors. with a toonshader, it will create more steps to your color, depending on the shadow steps you use (i prefer using only one shadow step). so for example your shirt is blue, and you have 2 shadow steps, your shirt has a blue, dark blue and darker blue color on it. it will look a lot more detailed than solid colors. so you dont actually need to add details onto the model / Textures when you use the shader.

but let me tell you something. i know your games graphic and i tzhink you should keep it like it is. the textures of the houses, woods, bottom, and so on is allready detailed, and the colors fits so nice. you shouldnt use a cellshader at all. just draw details and shadows onto the texture of your character, and keep the graphic look like it is. then even more people can play it, not everyone has a super good graphics card.