ESTA Application with previous Waiver for Drug Use

Before I became a british passport holder I applied for a US visa on my south african passport and admitted to having used Drugs in my early 20's.
I was denied the visa but was allowed to apply for a waiver which I subsequently was approved for and the visa was issued for 12 months.
6 years later I acquired a British Passport through my mother and now I need to travel to the US for Work and Training.

I would like to apply for a ESTA but do not know how to answer the questions.

The first question is the one the asks if I am drug addict, which in my eyes am not but I do not know if the Americans consider me to be one.

the Third question, “Have you ever violated any law related to possessing, using, or distributing illegal drugs?”
Technically seeing as I admitted to drug use which is illegal i should answer yes to the above
question?

Question 7, “Have you ever been denied a U.S. visa you applied for with your current or previous passport, or have you ever been refused admission to the United States or withdrawn your application for admission at a U.S. port of entry?”
I assume I should answer yes to the above question as the visa was initially denied but then issued?

any advice on the way forward would be appreciated, I would Ideally apply for Visitors visa on My South African passport to avoid having that waiver in my british passport.