Is it obligatory to give sisters their share of the house's full value after it has been rebuilt with the son's money, or is their share limited to the value of the land only?

What you built can be interpreted in two ways:

First: That it was a gift and a donation, in which case it becomes part of the father's inheritance and is divided among all heirs, and you have no more right to it than they do.

Second: That it was with the intention of claiming the building costs, in which case you are entitled to take these costs, and then the house is divided among the heirs.

The matter depends on your intention at the time of construction, and it is not permissible for a person to retract their gift, except for a father regarding what he gives to his child.

The deceased's knowledge of their family's affairs is part of the unseen, which can only be established by a textual proof.