Another hand to hold here Whirliwig! I have a similar-ish story, with a happy end to the story...so hoping this will provide you with some positive encouragement!
My DS was a very fussy eater when he was younger (now 10). Until about the age of 8 he would only eat certain meals...like yours, about 8ish meals (was happy to eat as much fast food and sweets/crisps, etc!! Typically!) He wouldn't touch fruit or vegetables.
This really frustrated me. I tried the "well this is the only thing to eat", but couldn't face giving him nothing to eat. I read many articles on what to do and the method that worked was a long process and caused much frustration but ultimately worked!
I kept offering him to try new foods, vegetables or fruit. If I was preparing a vegetable, I'd ask him if he wanted to try it. He'd say no. Articles I read said that you have to offer them a new food several times (maybe 10+ times) before they will try it. Eventually, he tried it...and lo and behold, he liked it! I'd let him try a small part of my dinner. Most of the time he said he didn't want to.
The thing is not to be too pushy about it. That's whats so frustrating! In my experience, you have to offer it to him with no pressure. If he says "no", then it's a smile back and a "that's ok" reply. Softly, softly! But you keep asking (still with no pressure).
Eventually (this took around a year....so long process!) he eats more or less anything!! There's very few meals he won't eat. There's very vegetables he won't eat - he even likes sprouts and cabbage! However, he still won't try fruit (but hey, he's eating veg!) He now echoes what I've been saying all along "it's good to try new things!" He's even eating fresh mussels and sushi!
Like I said, it's a long, frustrating process. I tried to make his plate of food look entertaining, like creating a face, etc. Calling broccoli, "trees", cauliflower "snowy trees"! But now he's eating a huge range of food.
I hope this is of help and encouragement for you.