Curious to see how this ends up. We have done this many times, and no problems. My understanding is that you can not use DFVC if you get a DOL letter.
File an amended return and check the box DFVC, and pay the $750 as this is much more reasonable than $250 per day.
After having many bad experiences as well as time wasted answering numerous IRS letters for the same client (letter, response, letter saying they never received a response, etc, etc), $750 is worth not having to deal with this.