Updates:

i just spent 2 hours with flying blue, the agent suggested me to book award ticket one way from lax to ams for 62500 miles each plus tax, and she puts a remark for able to change and cancel on tickets. Then i got all 3 business award tickets already with separate booking code. After connected with KLM, they want $6700 extra to cancel the outbound ticket as the ticket difference. Connect back to flying blue, they said they can't do anything, apologize about didn't mention for extra cost, and they couldn't do anything beside cancelling my award tickets.