Where can I find wholesalers of flour?

What is the difference between Canadian all-purpose bleached flour and American all-purpose bleached flour? All of my baking using American flour comes out dense and heavy. Is there anything I can add to rectify the problem?

I'm making jam drops with my kids and I only have self raising flour in the pantry can I use it instead of the plain flour and baking powder?

Most of my cake recipes call for plain flour. When I use all purpose flour my cakes do not turn out the way they used to. The cake is not as fluffy as it used to be. Should I add baking powder to the recipes?

I have some flour stored in an unnamed container. Is there some way to tell if it if SR Flour or Plain Flour apart from cooking with it?

I am opening a cd store and I am having trouble finding wholesalers, suppliers for my inventory. I tried several searches via google and other search engines and have found very little 2 or 3 shady wholesalers that about it. Any advice?