What Beth said. You can't re-take the Steps once you've passed to try to get a higher score. It's not like the MCAT or GRE or the like. Plus, if you've already taken the Steps that by default you must already be ECFMG registered. (Which is why it's a little baffling that you've taken Step 3 already, because that means that you have to already have been licensed somewhere in the U.S.
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I think if you've already been practicing, your best bet is to try to contact programs directly, or with the help of an agency, and see if you can get a spot outside the Match. I think you will likely have to take what you can get, especially if you need a visa. Be prepared to have to have to relocate, literally, anywhere in the U.S. that has one open.
I don't think going back to medical school, which is what you are suggesting, is a viable option. Just my $0.02. Take it for what it's worth.
-Skip