You dont need a publisher, in fact there is no reason for it, unless they willing to pay money and marking you going to end up something like in youtube publisher scams. Also this happens a lot in books, games, local businesses, music, anything and anywhere that is popular. The only way to seal the deal is with a contract, you have to read it all because sometimes they will cheat you out of money. Having publishers doesnt mean it's a good thing either, you can be limited by creative, regain, laws or worst. Again there is no reason to join a publisher unless you sign a fair agreement.
steam wish list isnt accurate either, 400 of what is what you should be asking. Many groups have robots who auto subscribe when a new game shows up. You also have to consider if some of them will pay full price, i am guessing like every steam dev, you'll offer a discount. You shouldent offer discount at the very start that is bad marking, if you do such a thing than people wont buy the game at full price. Steam is also not the place to sell your game, many gamers there want discounts and if you not ready to lose a few $1,000 because of these gamers you should not be selling on steam.
this isnt about the game, its facts based on numbers. i do not know where you getting misleading information about facebook and steam but many developers have express trouble and all come to the same problem of facebook and steam playerbase. Also on to the fact that any good PR would tell you the risk of joining these companys. Facebook is in deep trouble with the US gov, possibly getting the book and splitting up to stop facebook monopoly and twitter along too. Steam is a way worst trouble with many countrys suing Valve for breaking their laws. You can not trust Valve to follow laws after many, many, many lawsuits that do show Valve being guilty . There is still one with gambling and guess what happens if Valve is guilty of making kids play gambling games, you guess it, they either shut down or your games get shutdown.
think what you doing, find reliable sources not from facebook or Valve, i been doing this longer than you can guess. gamedev is tricky and many times you find yourself with bad companys, you should always do things that support gamers never the wrong way.