Re: CGT
There is no Capital Gains Tax payable on death. Death is not regarded as a disposal for Capital Gains Tax.
If a person receives a gift or inheritance of a house which they have occupied for at least three years, they are exempt from Capital Acquisitions Tax, as long as they don't have another house.
In your case, if your partner dies, I don't think that you will qualify for the exemption as you already own a house. But, I don't know. Contact the Capital Taxes section of the Revenue. It's a straightforward question and I imagine that you will get a straightforward answer.
If you are subject to tax, you will pay 20% of the value of the property received. ( First €23,000 exempt). It's not nice paying it, but it's certainly not the end of the world. I would not recommend getting married to potentially avoid this tax.
Brendan