As far as the share of your deceased elder brother is concerned, since your father has done a registered settlement with him, you need not worry about the claims of his wife on your father's will.
it is natural and logical that your father has settled your brother's account when he was alive and then wrote a will in the name of remaining legal heirs.
On the UDS Part, you can go in for a rectification deed in the registered office . Rectification deed is nothing but correction of errors/mistakes in the original registered partition deed. that way your fears will be taken care of and for rectification deed, the stamp duty and registration charges are very minimal. (for new settlement deed, you have to spend on stamp duty and registration charges again, which is not required if you do a rectification deed).