1 It looks much stronger evidence, yes. Are you selling property / closing out a lease? Evidence of that would help
too
2. IO could require your USC spouse actually establish herself in the US, yes , but my sense is that if this was going to be required then it would have been part of the rfe. However, her returning now and being able to gather further evidence such as state ID or drivers license, cell phone contract , employment letter etc would certainly be the best documentation
3 many spouses return for the 3-6 months before the beneficiary’s interview for this reason. Some consulates require it
4 the time limit is as stated in the letter you were given
5. dont delay.. gather and send assp