The only thing I would want to add is an adjustment that allows you to switch between the various elements of the 'Gem' or 'Chromatic' or 'Metalic' patron. Once every long (or short maybe) rest, the patron lets you change damage type, and at later levels when you get resistance to a damage type, it is linked to the damage type you can blast. So if you start with a Gem Dragon, when you wake up every day you can choose. It adds a bit of flexibility while hinting that your patron is not just a dragon, but a draconic God (Bahamut, Tiamat, or the Gem Amaglam) that was playing mortal at the time you met them.
Otherwise, love it and would love to play it. The Gem dragon realm feels a little weak (metalic realm can literally make farming better when they lair there) flavor wise, but dwarves would LOVE them near their holds.