How should I cite a paper that I've obtained by asking the author to send it to me?
It doesn't matter how you got the paper. Just cite it as you would anything else. I've had papers from Science sent to me from a friend when our departmental internet was down, but that doesn't change how I cite it. Yea, the journal is obscure and others will have difficulty finding it, but in theory they could given the info you provide. That should be sufficient.