Hey G,
I took a quick look at your Website and link profile.
There's no much I can suggest other than continue working on your site. The on page grader is just another metric, but you can't take that and expect higher rankings.
Google say they consider over 200 metrics to rank Websites, not only links, but also content, navigation, user interface, etc.
If I was required to suggest you changes these a few a would start:
- make the site on HTTP or HTTPS. There's no reason to have only your homepage under HTTPS unless you transfer sensitive data over a form in that page (password). You have the sign up and sign in forms, both using a target script that is under HTTPS, but no other page actually requires HTTPS. I would personally go with everything HTTPS. While we are on this, Godaddy certificates, while cheap are insanely slow. I mean, each time a user request a page under SSL, it needs to verify the certificate with Godaddy's repos, and theirs is slower than several other issuing entities. I guess that's because the amount of certs they have (given the price). I would choose to use a better provider.
- Are you using some kind of HTML compressor? I guess you are because of your output. Have you considered using CloudFlare? As you will probably leverage from several of their features, like file catching (none of your images is being cached).
- Consider writing a blog, creating content that others can use and then link to your site. You already have interesting links, but getting new on a daily basis naturally will help a lot.
- Check your HTML, there are some html errors.
- Check your competitors, what are they doing that you aren't? (except of shady SEO techniques).
As for the 301, it is perfectly implemented. Your robots file has nothing in it and does not need to. You can probably add (and remove everything else in the file):
User-Agent: *
Allow: /
But it wouldn't help much or even anything.
It will require a much more in-depth research, you may want to hire a professional SEO to look at your site and competitors'. I based my quick review only on your site, I don't know who your competitors are or what keywords you are targeting.
Hope that helps, a bit at least