Oh wow you do seem to be very stressed and I'm really sorry about the dress situation. However, I think that dress looks great on you and would be perfect for the wedding.
I don't think that will look bad at all, and if he looks good and it's what he really wants I don't think there is anything wrong with it, especially being a linen suit since that will be a little cooler.
After you sent me this link Meg I sent it on to my FMIL who I think is going to start doing it soon, and I really want to give it a try in a few more months. You've done so well on this diet!