Help with Fiancee Visa

Hello all, I'm Malaysian and engaged to a British guy. We're looking to get married and for me to settle in the UK so we're trying to figure out Fiancee Visas. We fit the financial requirements and I have a certified degree taught in English, so we're fine there. But I need some help in other areas...

1. Does anyone have examples of proof of relationship?
We've been dating for about 4 years and have photos and chat logs to prove it, but I read somewhere that's no longer enough. I read it's better to have shared financial responsibility like a joint bank account. Is that true?

2. Can I stay in the UK while I wait for my application to be approved?

3. Can I apply from within the UK on a visitor's pass?

4. If I manage to get a job there before my Fiancee visa is approved, can I have my work permit switched to a Spousal visa?

Thanks everyone!!