Hi there,
I can help you setting up Petition Exchange. I work with Digital Droplets all the time and I can asure you I will set up a server with all your requirements.
I will set it up on an ubuntu server, which I will set up from scratch to install latest versions of Ruby, Rails, Redis and all the requirements.
I have all the time to work on this, I have no more projects to do and my only job is doing projects on FreeLancer.com.
I'm really good at system administration, however as per the other requirements on your project, I won't lie to you. I'm not good with APIs, for that I would suggest you hire someone who actually do those things, like a programmer. My area are managing servers.
Send me a message.
Have a good night,
Elmer Hdez.