How to disguise or even out the top of my head? Please help (Photo)

I believe what you are saying in that you would like the height at the top of the head reduced for a 'smaller head'. The sagittal ridge procedure you mention is when a very specific midline of the skull exists of which it unclear as to whether that is exactly what you need. That requires a front view picture to determine. I suspect in your case its is the overall top of the head that is too high in which case the whole top needs to come down within the limits of how much bone can be safely removed.