1. Bicker, banter, dirty talk. Lockdown's a crass, gutter-minded bastard and Swindle loves the sound of his own voice. There would be lots of conversation.
2. Lockdown. The dark gray face is nice but aside from that I think Swindle has a really unfortunate paint job.
3. They have to stay on each others' good side for the sake of their business relationship, so they don't really argue, even if they sometimes irritate the fuck out of each other.
4. I think either one of them would take it in stride.
5. There are always wars going on somewhere in the universe, so there's plenty of work for both of them and they get to be bros/fuck buddies/business associates forever.
6. Someone takes out a contract on Swindle, and the money is just too good for Lockdown to pass up.