@Alfa20 first of all, I have to wonder why you are open to such huge groups. with 16 guests the nightly cost for each is a mere $25.62. Of course you are going to attract bargain hunters! These are the people who want everything free and nitpick no end. Lower your guest counts or add a nightly fee for each guest after a certain (much smaller) number and you will get a higher caliber guest. Trust me, I learned that the hard way.
As far as responding, I would just say::
"Hi--
Checking in to see how you preferred I resolved your requests. I want all my guests to have an awesome stay so I am willing to do X or Y. Please let me know how you would like to proceed by X time/date so that I can get the ball rolling. Thanks and hope that you are enjoying your stay!"
Keep after ABB but don't expect they will help in a timely fashion. Be prepared with solutions you are willing to offer and don't be bullied.