AF/KL doesnt work with standby pax except their own staff flying privately. You can not expect flying from a different origin because of AMS. Of course you can ask but I think the chances are slim it’ll be allowed without paying fare difference.

You can just fly to AMS and in case your AMS-HAM leg is canceled then you take it from there. Book a hotel or a train. It’ll work out.

have a safe trip !