1- I'd use 'when' as 'era' refers to time, but the distinction between where\when does blur a bit in such phrases.
2- I don't think it is a noun- it's a comparative adjective modifying 'ten years'. I don't think it's an adverb modifying 'live' here, but it could be in other case.
3- It's a bit of a mess because it shouldn't really be in a separate sentence. If you delete the full stop (period), you can trace it back to 'let you live... and not so sick....'