The "if's" of the three Elven-Rings

[Gorthaur the Cruel]

Ok I agree. So they were meant to fade for the doom of Mandos was inevitable.
But the weird thing is, Galadriel's ring intensified her longing for the sea. This was an unforseen side-effect (can somebody explain this side-effect?).
Some questions come to mind:

1.) Sauron being cunning, why didn't he do this (shared the lore of ring-making) in the 1st Age? He could've increased his power (perhaps to the level of Morgoth, since Morgoth was declining due to his excessive distribution) with this scheme.

2.) When Melian fenced Doriath with an enchanted girdle, did that girdle also protect Doriath from decays of time like that of Lorien (dual effects: preservering & protection against enemies)?

3.) When Sauron made the Great Ring, he put forth a major portion of his native power into it for it was said that the power of the elven-rings was very great & that which should govern them should be a thing of surpassing potency. So, I was wondering if the eleves did the same procedure, putting forth their native power as well. But if the Three were so mighty, I doubt that Celebrimbor's strength alone adequately supplied the Three's potency. Surely there must be more elves who poured out their essence. Anyone have an idea who these elves were?