It is not true that civilians will be killed if you don't approach quickly. You rather have to kill aliens quickly so you have to have good riflemen at long range. Of course,you can't fire when an alien stays out of your sight, but if it is far and out of sight civilians will be killed anyway, no matter how fast you move
Farthest one perhaps, but for those in the middle run-and-smoke extends the survivable area.
I still use one soldier with a shotgun and if he dies I can replace him with a soldier who has even very low close combat skills, but in battle I can use him as good as the previous one. This shows me that close combat does not require much skill and this is true not only in this game for me.
At point-blank range, accuracy changes little, of course. But at the limit of slug range it's not quite so easy, yet it's still close enough for plasma pistols and grenades, thus missing is very likely to get the scout killed either in RF or aliens' next turn. Not that hitting is guaranteed to help if the alien has armor, of course.
But the way RF works, the best solution is still to bomb the enemies into whom the scout ran with indirect attack from someone else - no line of sight, no reaction. I have one AR soldier following the scout and lobbing grenades as needed, and since GL has a decent range, especially with bounce mode, it often can help even if it's in the other team (on the closest flank).
For saving civilians, other than disabling aliens quickly, soldiers need to be visible so aliens choose to shoot at them instead of civilians. This of course conflicts with the need to keep soldiers to be able to attack.
That's where snipers help - they have to lag behind to save TU for shooting anyway and early on, the range gives them a good chance even against plasma rifles, once scouts and GL pick off the nearest aliens.
Always make sure uncovered soldiers crouch, there's a good chance shots will miss; better than for civilians posing in the open like shit.
Yup. Much like back in DOS game.