A collab does usually work really well in getting the word out that you have a product to sell, you have to be mindful that this genre (fat people) is quite a controversial one and people might not want to be associated with it.
If this was anyone else's game that you were working for I could understand your frustration. Right now though, the only person who's going to benefit from this is yourself; you're 'bending over' only for yourself ! That means you have to put in hard work but you also reap the benefits of that work (eggs your game getting published)
The way I see it, you're on a boat and there's a leak in it. Right now you're waiting for someone else to fix that leak as you don't want to 'do it for free' but no one is coming to your aide and you continue to sink. If you don't change, you'll drown and your game won't be published.
No one said a project like this could be easy, from what I've seen you've already done a good job at it, but it can't stop here if you're to fully succeed.
Good luck on it though