Lots going on here. I will try to catch up starting with:
The building blowing up.
There is a a small alloted amount of time where Neo can enter the first door and then enter the second door, from which he enters a third door, which is where Archie is. During the said amount of time the building will not blow up. After that time is up, you're on your own. When Neo exits the door, that alloted amount of time is long gone. Hence BOOM. So, the fianl words exchanged between Archie and Neo can be taking in many ways. Archie knows he will die if Neo goes through the door that leads to Trin. OR, Archie believes that Neo will not make it back to Trin to save her and Zion and everybody "plugged" into the Matrix will die becaus eof the "choice" that Neo said. YES, I said "Choice".
Is Zion not connected to a very large "generator"?
We have seen the water filtration pumps and such. these can be used as a source of power also, much like Niagara Falls powers much of Niagara Falls the city and many cities and town in that area of the U.S. So, Zion could NOT have a direct feed from the Matrix for a source of power and could servive on it's own if the matrix is destroyed.
Just to throw a bolt into a pile of nuts.
Tank says "Near the earths core, where it's still warm". In "The Last Flight Of The Osiris" (I can;t remember who) a crew member says "What's 4 kilometers down". Another crew member "Zion". 4 km is about 2 miles. that's not very close to the core, you think?????