I can answer portions of you questions, There are multiple slots that let you play through different countries but I don't know about manual save slots though. As far as catastrophic results, to my understanding it would be hard to fail at that level. One battle won't sink a Belle permanently (outside of death-dates). It's possible only if you take a critically damaged belle in to a fight but you will receive a warning if you attempt to (same for taking them out on death dates). The game is online only currently so most likely all progress is saved on line and is connected to your account and not your local machine. As for the kickstarter bonuses, it's probably one time use but it's to your whole account. So whenever you start a new game you still have the same belles unlocked for starters to each nation but the ingame currency (for example) won't renew.