Dear @Yangyudong.Liu,
I haven’t gone through all of your arguments, but the tower damping ratio inputs to ElastoDyn (TwrFADmp, TwrSSDmp) are explained in the following forum topic: Natural frequency and damping ratio calculation. To summarize, ElastoDyn uses stiffness proportional damping for the isolated tower with a fixed base and no tower-top mass/inertia.
Best regards,