Did you get Affirmation of Freedom to marry from yr embassy that states where you will get marry?
If you are willinng to try outside Bkk, it might be quicker. Try Samutprakran (สมุทรปราการ), Nonthaburi(นนทบุรี) or Ayuthya(อยุธยา) by calling them first.
I have noticed that it seems to take longer to complete this process. However, from cases I heard about, ppl just went to nearby provinces.
If your Affirmation states where you will get marry, you will need to ask first if another amphur will accept the paperwork.
In Thailand, rules are not always followed or adhered to. And rules can vary drastically. Just keep asking.
May I ask what option to choose for retirement (O-A)? Is it the one that says something about 90 days? Sorry about being a bit vague. I looked very briefly, got a little confused and have been busy with some urgent stuff.
Maybe try different programme rather than Chrome or Firefox, try Internet Explorer and vice versa. Or change from tablet or PC.
Best of luck. I am doing the same application for my fiance soon, too. He is likely going to be stressed out despite me having to do it for him anyway. ;)