The arrest of the CFO of Huawei seems to be more like the catalyst....i note that the arrest took place on Saturday 1st Dec (but public knowledge only known yesterday) so the dinner and agreement between Trump and Xi on Saturday must have incorporated this news (i'm sure they both knew about it).
Volatility IS good for competent traders... so long as it's not so "fast and extreme" that you can't cope with it.
I also found this to be somewhat useful, but this document is not dated. Not sure if it is current: https://www.cmegroup.com/trading/equity-index/faq-us-based-equity-index-price-limits.html It appears the overnight markets have a 5% limit with a 5 minute trading halt. Not sure though.