Sorry to learn that your visa was denied, Mike. Reading through the 'Refusal Notice', I see it contains the "usual guff"
as to the reasons for your request being
turned down ... based, mainly, on the authorities' (pretty much inherent) suspicions that MOST applicants will fail to return home following their visit.
... which isn't exactly fair to those
genuine applicants who have every intention of abiding by the rules. Yourself, for instance!
Alas, I'm not too primed~up on Tourist Visas;
all I really know is it appears to be the "luck of the draw" whether they're likely to be approved or otherwise.
... if it's any consolation, you're far, far from alone in your predicament. And it seems your best bet now would, perhaps, be to give serious consideration to you and Steve registering as civil partners - with him as your sponsor - to enable
you to apply for settlement.