My only surviving Islamic heir is my spouse; would my spouse take the entire estate?

Yes. A surviving spouse would take her prescribed share from the estate. A wife’s Islamic inheritance share would be 1/4 (or 1/8 if the husband had children) of her husband’s net estate. A husband’s Islamic inheritance share would be 1/2 (or 1/4 if the wife had children) of his wife’s net estate. The balance left in the estate would go to the decedent’s surviving Islamic heirs like parents, children or siblings.

What happens if there are no other surviving Islamic heirs?

Except for Uthman Ibn Afan, who held that a spouse is entitled to share in radd like the other obligatory Islamic heir takers, the Shāfi’ī, Ḥanafī, Ḥanbalī School and Mālikī Schools hold that while spouses are obligatory heirs (ahl al-fara’id), they are not entitled to radd. The majority of Muslim countries, including Egypt, United Arab Emirates and Jordan today provide that while they do not permit a spouse to take radd if there are any other surviving Islamic heirs, they do permit a spouse to take radd if there are no other surviving Islamic heirs. So if the sole surviving Islamic heir is a spouse, the spouse would take his or her Quranic share plus the balance remaining in the estate by radd.