The NADA is a law, and yes there is a lot of criticism to be waged at it, but nota bene it applies to fresh arrests, and was intended to assuage the blood lust of the Republican islamaphobia wing and justify their penchant for torture and rendition since it was the only way they could convince Fox News viewers they were tuff enuff.
(Yes, Obama signed it, but you should read his signing statement, instead of guzzling down whatever Greenwald's latest screed is.)
Point to hand: If Assange were extradited, that law would not apply. It would apply only if the Navy Seals swooped down onto the streets of London and kidnapped him outright. It applies to fresh arrests only, not arrests making their way through the legal system.
The treaty applies if the man is extradited, so the maximum sentence would be the sentence outlined in the extradition request.
I'd also like to make a point: IF the Navy Seals swooped down and kidnapped a notorious person, that might actually end up with a beneficial result. Laws can be challenged, and while the GOP is busy appointing as many unqualified judges who don't know constitutionality from a hole in the ground, we still have qualified judges on the bench. We could get that law overturned.
Other point to hand: This is an interesting read from a relatively neutral journo:
www.theatlantic.com/ideas/archive/2019/04/julian-assange-got-what-he-deserved/587008/