Fixer-upper, classical?

Hi, firstly let me say I am no guitar builder, I bought a guitar in a charity shop for a fiver and have methodically gone over it in the hope that I will at least save it from the bin where is was destined, or so I was told. I've glued brases, reglued the bridge, taken off a horrendous layer of gunk from the fretboard. It's a cowboy job but gawd help me I have fallen for the plank and am eager to breathe new life into it.

But...

The poor fool who had driven it into the ground before me had done it a great disservice by putting electric strings on it, I took one look at the headstock and thought... this is a classical guitar surely, and it needs nylon strings. So I bought nylon strings and since I had gone to great effort all round decided to buy a new nut, for a classical guitar. When it arrived it was about 5mm too wide. Then I started to look at the existing nut, it's 47mm wide. Now I'm thinking, why is the neck on this 'classical' guitar so slim, is it a classical guitar at all?

Now I think of it the body is pretty thin too, anyhow, can someone help? Is my guitar some sort of bastardised hybrid that has been messed with over the years? What kind of strings should it have? Can you get classic guitar nuts that thin? Basically... what have I bought? How old do you reckon? It was made in Japan, I realise its no Gibson, how can I trace the make? Most importantly, what strings should I have and where can I get a nut to suit, I'm very unlikely to want to make one out of bone...

Thoughts anyone? Thanks in advance, I'm new but my god, I'm keen