LOL on the possum!!! Yeah, one funny looking cat! We get those in our yard sometimes, and my doberman has chased quite a few. She has even caught a few, but dropped them right away when we yelled at her to, and we thought they were dead.....oh no. THey were "playing possum", and got up and waddled off about 5-10 minutes later.
When I feed Arwen outside, I always sit and wait for her to finish. Last year a big orange cat was trying to eat her food and peeing all over my front porch. So I got in the habit of staying with her while she eats, since she eats pretty quickly anyway. She now likes me to pet her back while she is eating, and this is something I NEVER thought would be possible.
I'm sure this kitty will warm up pretty quickly, since he is getting close to you. The first time Arwen let me pet her, I cried, I was so happy. It started with her doing the head butt to my leg and then I would reach down and pet her tail, and as long as she didn't see my hand going toward her, she was cool with that. It was funny though, she would not let us pet her back for probably over a year. Now we can pet her all over, scratch her chin, do just about anything but pick her up, that is still a no no. But we have come such a long way. I think it is awesome to see this whole trust relationship develop with a feral.