Ooh, that is a hard one. It looks like you've thought of all the points I would check, and you've reached the same conclusion I would: this bird is not obviously a male or obviously a female at this age.
Unless you think it's worth paying for a DNA gender test ( https://iqbirdtesting.com/ ) you...
If there is only one rooster in the flock, do you know what breed he is? (If there are multiple roosters then never mind, because we won't know which one is the actual father.)
I am asking because certain breeding combinations can create color-sexable chicks. That chick is one of the colors...