There are no BMD records for the periods.
All you can use are the parish records.
The baptism and marriage records have been extracted to the IGI, fairly accurately, so as they are not there the likelihood of finding them is remote.

You might want to look at Wills. There is one for Ann Cowin als Banks. It will probably tell you whether or not Thomas was alive at her death. This would help narrow down his death date - there are several possible burials.
There is an MI for Ann Cowin listed in the Onchan index which may help.