General

hmm... never thought about that, but +1 to interpreting smile as a mocking of some sort. Originates from lack of confidence.

To give a more distinct hint - you could start a talk about food with fatty stuffing his face. Something like "Do you know anything tasty in here? What would you recommend? What do you like most in that? etc..."

If heavily mixed with appropriate remarks - this might get really thick and almost straightforward.

I'm not really sure what advice to give but I know from my own experience, I tend to miss the clues a girl is interested till later, after the encounter. I also have a problem trusting that her interest is genuine. I tend to assume she's just being manipulative or just wants money or something. I don't trust myself to know who's real and who's just playing a game. So what could a girl do to show me she's genuinely interested... I actually don't know. That's probably something I need to work on too, but how?

I'd say don't bring up a guys weight. Heck of he's big than he's got some insecurities. Don't be too forceful or drolly because he manly think its a prank or fat shame. I'd say like anything else talk like a normal person. Ask interests and such. If you start a bit light n go heavy it'll make him feel like one of a kind.

The desire for additional dated can be clearly conveyed by saying you had a good time and would like to see him again. Physical attraction can be conveyed by words - complementing his eyes, contact - brushing his hand with yours, leaning in and sticking out your lips for a kiss, etc.