How to choose profitable bounty ? What factors we should analyse before pick any bounty 
First things first, you gotta know what kind of ICO you are going to participate in a bounty. Check first the composition of their team and how can their product compete in the market if there is already competitors existing ahead of their product. Read the whitepaper, roadmap, check their product on github, and a community-driven ICO are the factors that can tell you of a good ICO.
You have good points right there on how to choose a bounty. But then the question still remains if the team would pay its participants. Of course a bounty handled by a good bounty manager is also a factor in choosing a bounty campaign since after all, they are the one handling the bounty participants issue. A reputable bounty manager who most likely would pay or the reputation to always pay its participants would be a good option then. These managers I believe review the projects first before they would promote it.