OK, this is basic but I did tweak the Bloom in A:M Composite.

How can I get the alpha channel involved in a composite? As it is the only thing I can get from A:M Composite is a black background. I had to render a TGA with the alpha buffer turned on and bring both images into PhotoShop to get the white background.

I know I'm missing something, I just don't know what it is...

My camera has a white background, it just renders black.

Our images have premultiplied alpha (long story short this means that alpha of zero will make your colors black). To see your camera background color you can render with alpha buffers off, or you can composite back in a white image, or use a white rotoscope.