I know you too well sensei
Umm well lets get started.
How its created: Well its created just like all metals, you combined your fire and earth chakra together to form the metal and then, from what i know you expell it from your body or through the ground.
Uses: it seems like it'd be more used for defense than offense due to the nature of its sturdiness and strength. Being immune to almost all blunt impacts makes its a good defense against most elements. Although like all metals it can be shaped into an offensive property but i mainly see this as a CE that relies heavily on its defensive properties more then its offensive.
S/W: Adavanced fire elements such as Hell fire and Sun fire would be, to my knowledge capable of burning hot enough and fast enough to melt the metal.
Magnetism: Well thats self explanatory, its a metal
Ice: Although ice lacks the pure strength to over power Adamantine, it does hold the ability to freeze adamantine thus making it brittle. Id say only ice jutsu focussed around actually freezing the metal and less overpowering it could win. So really its weakness to ice is more dependant on the form of technique the opponent uses more than the ice itself.
Advanced Lightning: Well like most Metals Adamantine conducts electricity, but advanced lightning not only is extremely hot but has alot of destructive properties, by breaking down the bond inside adamantine and then hitting it with destructive force would cause the element to crumble.
Other CE: It seems that Adamantines main strength is its density and overall strength, putting it on par with Diamond and Ali's Tungsten means its one of the strongest metal known.
Str: Water: Well water would no only lack the ability to pierce through adamantine, but it also lacks the solidarity to stop Adamantine in its tracks thus making water a useless element in its presense.
Earth: Self explanatory as this is an Advanced earth and Fire based element, it goes without saying that in comparison to strength and power, Earth doesn't hold a candle to adamantine.
LIghtning: It seems you've reasoned that normal lightning would be unable to break the bonds of Adamantine, im assuming this is due to its overall density and structure that make normal lightning unable to break the bonds and thus stop the element.
Wood: Well wood, like earth lacks the density and defensive properties needed to withstand a brunt attack of Adamantine, thus making the wood its weaker.
Hows that Darling?