Eandz well done! You should be proud of yourself (and don't worry if you have a bad day and give in, we all do when we're tired etc).
I'm not sure what he can and can't eat but we cook lots of traditional style home-cooked comfort food (no good for my weight!) like cauliflower and broccoli cheese, stews, soups, bread and butter, cheese on toast, beans on toast with grilled tomatoes, humous and dips, poached egg and toast soldiers etc etc. there are loads of tempting foods that are as moreish as crips and pizza (and there's nothing wrong with the odd parcel of fish, chips & peas
).
Home cooking is really easy once you have a go and there are loads of receipes on mumsnet. We have a breadmaker, so make our own bread which is amazing warm from the 'maker'! Soups are also much easier to cook than you might think.
You can even get N involved with the cooking eg helping to prepare the veg, rinsing it and putting in the pan etc etc.
And I think Ninja's comment about having a bowl of fruit as only for me a great idea - they always want what doesn't belong to them.
I feel very positive for you. My ideas may not suit you or you may need to take things slowly, but I'm sure you have brighter days ahead 
Keep posting here!!