1) "to some degree" -- the next century will take more of a toll than the first two, in fallout 3 the vaults were decrept, ransacked, rusted, broken.. I mean, 101 (as corrected by someone above) was never meant to reopen and ingame they have dialouge trouble with generators and purifiers.. Vault 13 was never intended to be one and had failing systems.
Vault 111 wasnt designed for vault-tech staff to remain there indefinatley; after 180 days they could leave and the rest would be taken care of.

2. Well.. Yeah. But the quarters would be small, theyd have to live with a tonne of cryostasis pods they couldnt do much with, theyd have to become some genius autodidact to learn the vaults maintenance requirements, replacement parts, ect if they were to conduct maintenance.. Then you could never expand..

3. In cryostasis you dont eat or drink obviously.. You could assume that not even a supplement is given, since your character doesnt wake up with a hose in his mouth or.. Yknow. Because, you're frozen.

Prestons idea is to REBUILD society and unite settlements.. He cant do that by hiding in a vault with 4 other people and hoping for the best. I mean.. Sure, if you wanted to make a place in 111, wait for the mods. But in cannon (and me personally) seems like an awufl idea. Why build in limited space when you can make a giant, looming tower?

Albeit, Vault 111 could serve as a great refuge for settlers in the event of an attack by the Brotherhood of Steel or other individuals if they prepped it.

It's a Castle, really.

Stability and Security

On a serious note, if Bethesda wanted to do a cheap 5 dollar bit of DLC, I would love the option of an adventure where you can clean out Vault 111 of whatever horrible infestation has taken root and then remake the Vault into another settlement.

I'd like there to be a grave site for your spouse, though.

Because, it's not like you can just "scrap" her/him.

There's a water fountain outside the Overseer's office. When I drank from it (repeatedly), no rads. Ergo, the water filtration system is still working. But you're right about growing food supplies; concrete floors aren't very fertile.

And all a Raider/Brotherhood has to do is wreck the Elevator up, and it goes from a Castle to a Tomb.

The elevator, of course, which survived and is designed to survive a nuclear blast.

Just saying.

Not realy the blast was miles away from the vault.

Also the vault was easy enough to get into, just push the big shiny button.

The main problem is that once you close the door your stuck, when do you come out? Your cut off, your in a undersized vault that never had actual long term life Suport for its un frozen population of a dozen or so,and was basicaly a test to see how long current cryo tech could keep you alive before failing,