Can any relationship still grow in this situation?

I really don't intend to be mean, but how many times/ways does he have to let you know 'he's not interested'? He isn't being mean to you. He's simply stated his position...and now it's up to you to face reality. He KNOWS you like him...but, he's straight...or, not interested in you like that. He's left the door open for you to be friends, but you're not taking the 'hint'. If you keep up the pressure, you'll FINALLY get what you seem to want...and that's 'REJECTION'. I'd encourage you NOT to do that, but to nourish the friendship by trying to be a 'non-ual' friend. Try to give him some sincere compliments and 'be interested in things he's interested in'...and see if that doesn't improve the friendship. That he might one day like you better and 'try experimenting'...seems a pretty big leap...something I wouldn't spend any time on thinking it 'might' happen... You've stated you have already lost some interest...that seems a 'good' thing... Stick to just 'being friends'...