网友所说的get far (with)和get sb far (with)在词典中是有说明的，仅以韦氏高阶词典get词条为例：
always followed by an adverb
a [no object] : to make progress in some activity
He hasn't gotten far with the essay. [=he hasn't made much progress with the essay]
b [+ object] : to cause or help (someone) to make progress
All that effort didn't really get us very far.
所以，网友句中的further应该解释为副词far的比较级形式。韦氏词典的“取得进步,进展”和“使…取得进步,进展”应该是一种引申义。
牛津高阶(9版)get词条17解释为：[l]+adv./prep. to arrive at or reach a place or point 其例句为: I haven't got very far with the book I'm reading.这里的get far可以字面理解为“到达很远距离”，可引申为“取得进步，进展”。
此外，韦氏高阶对get有这样的解释：always followed by an adverb or preposition,[+object]: to cause (someone or something) to move or go，如果根据这个义项，get sb far可以解释为“使…移动很远距离”，引申为“使...取得进步,进展”。
至于句中get us any further，倾向于把any further解释为状语，表示抽象意义的距离长度，或一种程度，根据韦氏词典的解释，这种状语应该是必具性的。如果把any further解释为宾语补语，一般来说，宾语与宾语补语会构成逻辑上的主谓或主表关系，如果单独说we are far/further，恐怕不会成立。至于with词组，可以解释为谓语动词get或谓语动词及其补足成分get us any further的方面状语。
个人看法，仅供参考。
