1. Here they descripe how to draw an ellipse inside of an ellipse.
Perhaps it`s easier to draw the romb and the rectangle in one figure?
http://wiki.eclipse.org/GMF_Newsgroup_Q_and_A#How_do_I_draw_an_ellipse_inside_another_ellipse.3F
I had a simliar problem: I wanted a circle centered in a triangle. After
some fruitless approaches with one circle and one triangle I made one
figure where I draw both at once. First I draw the triangle, then I
calculate the radius of the in-circle and draw the circle accordingly.
That is also good, because then the circle becomes also bigger when the
triangle becomes bigger.