1) Like the original article, this leaves unary operators as an exercise for the reader (though it does note so explicitly and provides a small hint)
2) This looks more like Pratt parsing vs. the approach described in the article
3) I was asking the original author
See the "Other resources" section for other approaches to this problem.
1: https://eli.thegreenplace.net/2012/08/02/parsing-expressions...