Wow, Durness. I had one of the worst eating experiences in my life in Durness. It was a number of years ago so maybe things have improved!
The amount of land you need depends on whether you want an income or simply to grow enough for yourselves, and then, of course, what sort of income you can live with and how much time you have to invest in the land as against what you can earn working. I can earn much more working that I could earn from our one acre, unless I discover oil on it, and even in different cirumstances I don't think we coudl earn enough to live on even living pretty frugally. There are somethings I need cash for - wine and chocolate, fo instance. And insurance and vet's bills too. And I've never fancied woolen knickers!
If you haven't already got the John Seymour self sufficiency book, then get it. It's a bit extreme for most of us but great for musing over.
We'll look forward to sharing the dream with you!