Wait till your both on the sunny side of Lathe and Laythe is on the sunny side of Laythe, then burn for an escape from a ninety degree orbit, Jool should be about 90 degrees ahead of Kerbin in its orbit, this will give you the best shot of getting from Laythe to Kerbin in a single efficient burn, as for escaping Laythe and then dropping into a lower Jool orbit, at some point the gains from stuff like that just arent worth it, especialy since you have to escape from Laythe too, not just modify your orbit, also you are already deep enough in Laythes and Jools gravity well already.