I think you have to look at what you have today.
The house value is €165K.
You owe €80K, if you sold the house today you would have €85K in your pocket and no longer own a house.
If you go for this deal you still will no longer own a house and will be using this €85K to prepay your rent for an indefinite time which although unlikely could be less than 1year or could possibly more than 30 years, who knows.
The question you need to ask yourself is €85K good value for a lifetime tenancy ? if you think it is and your solicitor is satisfied that your tenure would be secure and without complication, then it might not be a bad idea as repayments of €1500 monthly from two state pensions is, in my opinion not realistic.
The down side of course is when you and Mrs Traderbill pass there will be no property in your estate.
Are your pensions contributory ? If so and if there is rental demand in your area, would the Rent A Room scheme be of any benefit to help with mortgage repayments ?
http://www.citizensinformation.ie/en/housing/owning_a_home/home_owners/rent_a_room_scheme.html