For a person to get an immigration bond, he will need to be done with any state proceedings against him (ie. a criminal charge). That may not be the case here but if so, that is why it takes a while to get an immigration bond. Once done with that, your fiance is entitled to move (file a motion) in the immigration court for a bond. As far as I know, the law says they are obliged to give a hearing within 48 hours but I have never had that happen. Its always slower. For that, you should have a lawyer.
To actually get a bond however, your fiance needs to be eligible for some form of relief. I could not tell you, based on the limited information you provided, which form would work, if any. A family petition is the one you suggested and there are a few rules about it so you should use a lawyer. I have done this successfully before in a case which sounds exactly like yours, and the couple are now legal and living happily in Virginia where I practice. Good luck with this.
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