Just a quick addition to answer 5. Since you earned credits from a chest, you must be in bronze league. The rewards for bronze are a little different and are detailed in a table in this post: https://peakd.com/splinterlands/@splinterlands/game-economy-and-reward-updates
Edit: Actually, those percentages aren't quite right for any league. Best to just refer to the link I posted.
They were top of my head numbers. The main emphasis was mostly you get lousy stuff. Sometimes you get lousy cards but there is always a chance of getting something good :)
Thank you, good to know, had wondered about that but forgot to ask =)