I haven't had issues, in '17 I would go into the apps on my phone and select force stop, allows game to stop all activity. The reopen it, if you have low storage space it can also slow the game down.
You cannot see the bonus ahead of time, some people in global chat say they know, but really do not. In 2018 so far, it's been nice each event has had a specific boost located in the news at 11am cdt
They do, certain tiers of each level (bronze,silver, gold, platinum, diamond). You get 3 of some sort whether it is Cash, Gold, XP, bonus games, draft picks.