The sister publication of Fan is, of course, Previews . Previews used to have a circulation of 100,000 to 125,000 per month, before the exclusive contracts. Their current circulation is anyone's guess. Its ad rates are very reasonable, but all the high-visibility ad space is reserved for DC, Image, Dark Horse, Acclaim etc. However, it does offer some very good ad rates, and a disproportionately large percentage of its readership are retailers.
Demographics are a mystery here.
In addition, there are many small, independent newsletters, and magazines devoted to independent publishing. You should check out the ones that apply. Production Everything you do with your comic that makes it more appealing to comic buyers is going to cost you more money. That, bluntly put, is the truth. Totally black, and totally white.