I finally got it working today,
But then it stopped working.
Here's the behavior:
I enter my pledge amount and then click FUND.
I get to a page to enter my address, I enter it and click "Fund this project".
Then it takes me back to a page that looks like a combination of the previous two pages: It has the image of the Project but has the funding amount controls and "Fund this Project" button.
After I got it working on wp2, I deleted the Fundrasing (and the wpmudev dashboard) plugin from the other wordpress installation /wp1/ - and now my wp2 installation doesn't work properly.
I'm not sure if this is why it doesn't work anymore, but it's the last major thing I did.
Other things I did recently:
I deleted the old projects that had already tested.