Definitely, Histon. I would believe William would have used Histon as his surname.
The subscription site Roots Ireland has an October 7 1859 marriage in Mahoonagh RC parish for a William Histon to an Hanora Meany. Hanora was from Dromcollogher.
There was also a January 19 1860 marriage for a William Histon to a Maria O'Donnell at Abbeyfeale RC parish.
Abbeyfeale/Dromcollogher and Mahonagh parishes are all located in southwest Co. Limerick.
No way to know what happened with Bridget from a marriage standpoint.