it seems we have clarity here. DL has many routes it sells here, but you don't want any of them, but rather routes that other airlines sell. While DL may prevail to get its own partners to open up availability, it won't on other airlines partners. And since DLs own partners have plenty of options for you that get you from your origin to your destination, that's all you can reasonably expect. I'm not sure what you are suing for, but small claims court does not provide injunctive relief/specific performance.

I Also expect your EU/UK 261 compensation claim to be summarily denied, as it does not provide a mechanism to force airlines to put you on specific flights. Even if you are entitled to meals and accommodation, you are not entitled to that until December.