I love Fabric.com although I will admit since Amazon took over things have changed (and not in a good way) I don't know what problems you have had with them, but I would suggest calling their customer service. I have had a couple of problems and they were very nice and helpful One time I got the wrong fabric. They replaced it free of charge and told me to keep the incorrect fabric.. which was awesome.
I never heard of Whittles.. I will have to check them out
Have you looked at Missouri Star? They don't have the selection that Fabric.com does but they have wide backing.