When you say "open rate" mortgage, we would say "variable rate" and the rate would reset periodically based on some standard index.

So the fire victims will require housing in the rebuild period. 

The contract promises to make payments to you over an agreed period of time.

Who noted that we simply have a porous basement wall, like every other basement wall from that time period.

Run the calculations on the expense of doing a refi at a slightly reduced rate vs. keeping the current loan for whatever period of time you think you will hold this house.

Period, end of story. 

That could involve mediation or court, OR possibly if nobody takes an action you may simply be awarded the EMD back after a certain time period.

I could put a down payment for a conventional (20-25%) 550k duplex, but I feel it could hurt my chances of buying as many duplexes in a 5 year period (for example) if I go conventional VS an FHA at 3.5%. 

There are some buyers that are just a complete terror during warranty periods with expectations that are not at all aligned with the purpose of a builder warranty.

If you're allowed to object and you're still within your objection period, you may want to review your title commitment for objectionable matters that may give you a right to terminate without penalty.