yes and no: Nanyue had been a vassal of the Han, but this title was just superficial. the country was independent, and never accepted orders from the Han emperors. Zhao Tuo promoted himself to emperor, a concept clearly derived from the Yue/Viet people that strived an equal relationship to Han China.
you may be right. at one point, the Yue nobility intrigued and went too far by rejecting further paying tributes. The Han used the provocation as pretext and annexed Nayue Kingdom at the end of the day.
Yes they did accept orders Zhao Tuo ceased his attacks against Changsha and Zhao Tuo himself apologized for his invasion.
Though privately he copied the concept of Huangdi,he used the title Wang when Han envoys came showing his submission.
Huangdi is a Chinese title not Vietnamese,declaring independence is not a Vietnamese trait.
Zou Ying of Minyue attempted to attack Nanyue leading to Han intervention after Zhao Hu pleaded for help.
Furthermore as act of good faith Zhao Hu sent the crown prince Zhao Yingqi to the Han capital,in turn Zhao Yingqi sent Zhao Cigong as his father did to him.
The reason why the Yue nobility began its overtures of rebellion is because Zhao Yingqi married Chinese woman surnamed Jiu.
Empress Dowager Jiu had an affair with Anguo Shaoji(Chinese) leading towards the native Yue people to look at her in disdain.
Later Anguo Shaoji's suggestion that the Nanyue court be treated as a normal feudal lord ie like Wu Rui of Changsha rendering tribute every 3 years etc. which angered the Yue minister Lu Jia.
Empress Dowager Jiu held a banquet where she tried to kill Lu Jia leading to his escape however nothing happened since Zhao Xing still relied on his support.
The straw that broke the camels back was when the Han emperor sent Han Qianqiu and Jiu Yue with 2,000 men to dispose Lu Jia.
Lu Jia preceded to eliminate the Queen dowager Jiu and other Han envoys,Zhao Xing was deposed and Zhao Jiande was made king.
Lu Bode,Yang Pu and some Nanyue traitors preceded to march towards Nanyue.
Eventually Zhao Jiande and Lu Jia were captured however their fate is unknown.