The place of birth for Thomas on the 1851 census, which has been transcribed as 'comlferan' looks like a squashed together Ireland, County Cavan to me which make more sense...the 1891 census also has Cavan Ireland as his place of birth.
What occupation is given for Thomas snr on the marriage cert ?
There are about 30 church of Ireland parishes in County Cavan, not all have records available going back to the 1820s. A search of the baptism records currently available online shows no promising matches of a likely baptism of your Thomas that I see..
Do you know the names of any possible siblings to Thomas jnr. - e.g. other Hustons from Ireland as neighbours, witnesses at his marriage etc ?