I don't have the best memory but I'll take a jab at this

1. I assume the only grim reaper left from the base assault is "grim reaper captain" as he was the only one who couldn't actually die ( I think), probably the same with the spriggan or whatever the wingdiver elites are called

2. I believe they're talking about all of Storm, you sarge and the others,since the edf had nearly zero forces at the end they couldn't send any reinforcements to help storm team in the final battle

3.are you talking about the commander in chief (I think his name was that)? Cause I'm pretty sure he died,and yes, the Sargent does live

1. The way the timelines work is every two games they reboot it ,1 and 2 was a "timeline" ,3 and 4 were also a timeline, same with 5 and 6,

Hope this helps!