There is indeed a better way to do this:

Look at the curve object. It has methods to retrieve tangent and normal vectors at any given point of the curve. The values are exact, as there is a way to mathematically calculate these without any approximation.

Thanks once again for the help!

the Stitch-script on this site uses getNormal() and normalize() for this.

example:

var art = new Path();
art.moveTo(500,500);
art.curveTo(500,250,250,500,250,500);
var art_copy = art.clone();
art_copy.curvesToPoints(50);

/* 
curvesToPoints() used for this example, 
but this doesn't give you a nice distribution 
of points along the path.
*/

var count = art_copy.curves.length;
for (var k = 0; k < count; k++) {
	var res = new Path();
        var bezier = art_copy.curves[k];
        var pt = bezier.getPoint(0);
	res.moveTo(pt);
    	var n = bezier.getNormal(0).normalize(10); 
    	// normalize(10) = offset from shape : 10 pts
	if(n.x != 0 || n.y != 0){
        	res.segments.add(pt.add(n));
	}
}
art_copy.remove();
activeDocument.redraw();