We are currently working very hard to solve both of these issues. I have been sitting in-front of my computer for the past 6 hours restarting the server every time is has gone down. Please be patient while we work out what is causing the crashes. If everyone behaves there might even be some rewards as a result of your patience.
A reminder that we are currently running the FTB Ultimate pack. I have noticed many people try to connect with other modpacks in the console.