Here are some additional information that might be helpful.
1. Under IRC section 1014(b)(9) - any property that is required to be included in the value of a decedent's gross estate for estate tax purposes shall receive a stepped-up
9) In the case of decedents dying after December 31, 1953, property acquired from the decedent by reason of death, form of ownership, or other conditions (including property acquired through the exercise or non-exercise of a power of appointment), if by reason thereof the property is required to be included in determining the value of the decedent’s gross estate under chapter 11 of subtitle B or under the Internal Revenue Code
of 1939. In such case, if the property is acquired before the death of the decedent, the basis shall be the amount determined under subsection (a) reduced by the amount allowed to the taxpayer as deductions
in computing taxable income under this subtitle or prior income tax
laws for exhaustion, wear and tear, obsolescence, amortization, and depletion on such property before the death of the decedent. Such basis shall be applicable to the property commencing on the death of the decedent.
2. According to IRC section 2036 - the full value of the property in the retained life estate - is subject of inclusion into decedent's gross estate.
The value of the gross estate shall include the value of all property to the extent of any interest therein of which the decedent has at any time made a transfer (except in case of a bona fide sale for an adequate and full consideration in money or money’s worth), by trust or otherwise, under which he has retained for his life or for any period not ascertainable without reference to his death or for any period which does not in fact end before his death— (1) the possession or enjoyment of, or the right to the income from, the property, or (2) the right, either alone or in conjunction with any person, to designate the persons who shall possess or enjoy the property or the income therefrom.
3. Therefore under IRC section 1014(b)(9) you should have a full stepped-up basis for the life estate deed.
I hope that helps.