GDP does not equate to government revenue. The expenditure to GDP is irrelevant. GDP also considers government spending and it’s easy to inflate the number when a good chunk of it is borrowed money [1].

I agree with (3) but don’t think (4) has substance. “Fair share” is subjective never used in good faith.

[1] https://www.imf.org/external/datamapper/exp@FPP/USA/FRA/JPN/...