Tradition was to marry in the bride’s church, so Annahilt Church of Ireland could be where Mary Jane Spence was baptised. Unfortunately save for some fragments, that church’s early records were lost in the 1922 fire. The fragments that survive are: Baptisms, 1784-91; marriages, 1777; burials, 1784. They can be viewed in PRONI.
Griffiths Valuation for 1863 lists 2 Henry Spence households in the parish of Annahilt. One in Ballylintagh was a labourers cottage, as was the other in Carcagreevy.
No Henry Spences farming in Annahilt in the tithes for 1829:
http://www.irishgenealogyhub.com/down/tithe-applotment-books/annahilt-p…
I also searched for William Houston farming near Slemish. All I could find in the tithes was a John Houston farming in Carnstrone & Douglas in 1825 (More commonly called Carnstroan):
http://www.irishgenealogyhub.com/antrim/tithe-applotments/skerry-parish…
That Houston family had left or died out by the time of Griffiths Valuation in 1862. Carnstroan is right beside Slemish. It’s in Carnstroan townland. (The road up to the public car park is Carnstroan Lane).
There are several Houston gravestones in Broughshane 1st Presbyterian graveyard and Racavan, both in Broughshane town. None has the names associated with your family. No Houstons stones in either of the Buckna graveyards.
Likely churches for the Houston family if they lived beside Slemish are Buckna Presbyterian, Broughshane 1st Presbyterian & perhaps Glenwhirry. Unfortunately none has records for someone born c 1826. Jane Devlin’s name suggests she may have been RC. If so Glenravel’s parish records start in 1825, which again is not early enough.