difference - 'of which' in 'to the utmost extent of which' (1906 UK)

Source: p 279, The Family, by Helen Bosanquet, BA in Moral Sciences (First Class; Cambridge)

"If the husband is the head of the Family", she continued, "the wife is the centre.
It is she who is primarily responsible for the care of the children;
to the utmost extent of which the family means will allow,
it is her duty to see they are well cared for, both physically and morally;
and it is generally agreed that this duty can be properly fulfilled only by personal attention.

1. Am I right that which 's antecedent is the care of ... ?

2. I can't pinpoint why, but of which bothers me. It feels redundant.
What would differ if of which were removed? Please explain?

Footnote: I encountered the above on p 28 of 296, Understanding Housing Policy, by B Lund.

Answer

Helen Bosanquet BA in Moral Sciences 1906 was using a verb allow of which peaked around 1700, then fell off, and then enjoyed a little renaissance around 1850. It means 'to allow'.

So the clause could be rewritten:

To the utmost extent which the family means will allow of, it is her duty to to see...

To the utmost extent of which the family means will allow, it is her duty to see...

In contemporary English using allow instead of allow of:

To the utmost extent which the family means will allow, it is her duty to see...