Okay, cool, those are your opinion. There is no common ground on these definitions. I may agree with many of those, I may not agree with others, but after all these are just our opinions.
We both know that different people use these terms differently. The German political education ministry for example defines extremism as any anticonstitutional movement, and goes on to mention “caring too much about anti-fascism” as a form of left-wing extremism: SourceMeanwhile, they define radicalism as an ideology unwilling to compromise their positions… or someone who seeks to combat the root of a societal ill. Source
On the other hand, the ADL defines extremism as any belief outside of the mainstream, and even “conflate” it with radicalism: SourceMeanwhile, the British government considers extremism to be anything opposed to “British values”, whatever those are, along with specifically mentioning people who condone the loss of British soldiers: Source
I am sure that many, many people would disagree with these definitions both inside and outside of these countries, let alone across political ideologies. No matter how strongly you feel about defining these words to your liking, fact is that they do not have clear definitions and are useless in any kind of serious debate. As long as a pro-capitalist queer activist is considered left-wing by about half the population and right-wing by the other, there cannot be common ground.