Well, after plenty of Googling, I found that there really was no error. All the code was correct, all.. pretty much everything was correct. The only thing that was wrong was that it was off by 90 degrees. This thought had crossed my mind multiple times, but every time I looked at the dot and the line, it just didn't seem right... The fixed code is below:
public static float getAngle(Point source, Point destination) {
System.out.println(source + "\n" + destination);
double xDiff = source.x - destination.x;
double yDiff = source.y - destination.y;
System.out.println((float) Math.toDegrees(Math.atan2(yDiff, xDiff)));
return (float) Math.toDegrees(Math.atan2(yDiff, xDiff)) + 90.0F;
}
For some reason, I feel like I've just dropped a couple IQ points for overlooking this multiple time.