Hi CT

Don't give up just yet! I hope we will be able to find something of Patrick for you.
The facts that I can glean from what you've posted are:
d Dec 1869, 85 yrs =
birth 1784 (death cert and headstone)
m 1835 (marriage cert) OR 1827 (from death cert)
imm 1813 (if 56 years before death)
OR 1828 (if 41 years before death)
b 1793 (if he was 42 when married in 1835)
OR 1784 (if he was 42 and going by death cert marriage date of 1827)
The only dates we are definite on are his death, 1869, and marriage, 1835.
The immigration date is the most uncertain, with a 15 year difference between the two dates suggested by the death cert.
The birth date is uncertain, but less so, with 9 years difference between the two possibilities.
It all hinges on whether his age at death was accurate or not.
let's say he was 42 when he married in 1835:
he would have been born in 1793
he would have died aged 76
There is the 9 year gap again!
As for his immigration, I would think the earlier the date, the more likely it is that he was not a free man when he came out here. Free immigrants did come out early on, but it was more common later, particularly as assistance schemes were introduced.
I don't think I've helped much here, but I was just trying to get all the dates and ages straight in my mind.
Prue