However, this time, we gave ourselves one week due diligence, had an unexpected trip that shortened our time more and then began to question our understanding of the 1% rule and if it really applies to duplexes - which thanks to all of you and others locally - we learned it does not.

This isn't a situation where you are likely to have negotiating power, so don't bother trying. 

You need staying power. 3) Only you can decide what works best for you.

I am constantly amazed at the power investors give up to their property managers.

Multiple business entities each have their own purchasing power once their credit is established and there are ways to do that.The second is protection against liability.

They often have to have a safety inspection by code enforcement before power will be restored, and often there is so much garbage and vandalism but they are not condemned.

Cash is powerful, and learning a market takes time. 

Probably a special power of attorney would do it but I would think someone licensed to manage property wouldn't have to jump through that hoop in most states.

That's the power of debt.  

Since she is a dual agent, maybe try an appointment with her managing broker, bring a letter in writing and be prepared to discuss that you felt you were pressured into making the offer with the high earnest money deposit and no contingencies (especially if that was the agent's idea and not yours) and that you feel the agent should have pointed out the high-power wires so close to the property (although since they are right there, you probably should have noticed them yourself so not the best excuse), that apparently there were many offers so the seller should not have much trouble selling to someone else quickly and that you want the contract released with your full deposit back due to feeling like you were not represented to your satisfaction and didn't really understand that she was not representing your interests.