Can Chinese with SpanishPR apply for UK spouse visa in Spain

[shalom2all]

Hello everyone, just new to the big family here

If possible, I need some help about my case, thanks a lot:

Case:
My wife is UK citizen and I am Chinese but holding a valid Spanish PR. Now I am staying in UK with 6-month family visit visa. When my family visit visa is expired, I want to apply for UK spouse visa to stay with her still.

Question:
1. Can I apply spouse visa in Spain or should I back to China for application then? (although I prefer in Spain)
2. Which documents are required if I apply in Spain or in China?
3. How long does it take when I apply in Spain or in China?

Thanks again for your kindly help Cheers..