1. They might not, but legislators shouldn't stop making laws for their own state because they're afraid the Supreme Court might overturn it. They might not even take the case.
2. Maybe! Maybe they just want to limit the amount of semi-automatic rifles on their streets. They did just have a mass shooting in Highland Park last year, in which the shooter used a semi-automatic rifle with high-capacity magazines, so it's understandable that they would want to do *something*.
3. Because mass shootings do a lot more damage to society than just the body count. They shock and terrify *everyone*, threaten even the most peaceful and innocent among us, so that no one is safe.
4. They do, but so do Tommy Guns, and they have sat comfortably behind the Class 3 license wall for almost a century. The government is allowed to limit rights when they conflict with those of others.
Either way, it will only be of limited help as long as All-Guns-All-The-Time Indiana is just an Uber ride away.