: Why would he make a Ring knowing that the One, were it to
: re-surface, would be its master?

For a long time he didn't know that the One WOULD resurface. And having studied only the Ring-lore of Sauron, he does not seem to have been capable of devising his own Ring outside the laws governing those of the Elves.

: Perhaps he thought that the one was lost forever?
: Perhaps, in his studies, he discovered how to forge Rings of
: Power which would not be subject to the One?

No such Rings had ever been forged. In fact, the One was made after the others, and its secrets were not shared with anyone. So Saruman was at a great disadvantage for creating a Ring of Power that would not be subject to the One Ring.

: I favour the last option. A number of Rings were forged before
: the One and, indeed, before Sauron had a hand in instructing
: the Ringsmiths. I think (and it's just my opinion) that Sauron
: forged his Ring specifically to control the main Rings of Power
: that he had been involved in making. He could 'read the minds'
: of the wielders of the Three (and vice-versa, according to
: Galadriel) but not control them. Saruman must have known about
: this and therefore was not worried about being controlled.

He would have been able to control the wielders of the Three just as he would have been able to control the wielders of the Seven and the Nine. But the Elven keepers ALL took off their Rings when Sauron put on the One Ring.

: However I don't know why Saruman's mind wasn't laid open to
: Sauron as soon as he began to use the Ring. Or perhaps it was,
: and that, along with the use of the Palantir was how Sauron
: overcame him.

Sauron did not possess the One Ring, so he could not directly use its power to gain control over Sauron or the Keepers of the Three. But Sauron did indeed gain considerable (if not complete) mastery over Saruman through the Palantir.

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Parma Endorion: Essays on Middle-earth, Revised Edition