While possible, a dragon of that age should have the following spell list available to him (or at least something comparable)---(unless the curse really is that bad):
1–endure elements, mage armor, divine favor, cure light wounds, shield; 2–bull's strength, cat's grace, blur, endurance, fog cloud; 3–haste, dispel magic, protection from elements, slow; 4–spell immunity, dimension door, improved invisibility, detect scrying; 5–cloudkill, righteous might, dominate person, teleport; 6–heal, greater dispelling, harm; 7–spell turning, destruction.
So he SHOULD technically Heal himself while he's sitting in his lair and at least put up a protection from elements (cold), if not a detect scrying and a spell turning as well.
The second the cloudkill drops on him he'll take the piddly d10 then greater dispel it. Protected by the wall of force that you cast he can buff (bull's strength, mage armor, cat's grace, divine favor, protection from elements (if it isn't already up), endurance, righteous might, spell immunity, and improved invisibility) then fill the wall with a fog cloud so you can't see. Then teleport to the rest of the party, slay the remaining standing members. And wait for the mage to figure it out and come running to your fully buffed bad dragon-self with your readied greater dispelling for when your blindsight picks him up.
But again, this dragon is cursed, so it might work.
Enervations he can Heal, Cold he can protect himself from with protection from elements, blink he can dispel (along with everything else you got running--(1d20+15 vs DC 23 = 8 or better on every spell you've got up), and we haven't even gotten to his buffed melee attacks, breath weapon, or destruction spells he can toss around. I mean, if the first 3 spells you throw get turned back at you it could be over right there. 300 hit points you don't have.
But this is a heroic charge for vengeance with little chance of survival. So go ahead and take a stab with the hasted dual cold rays and hope you get lucky. Of if you've got twin spell, go with twinned ice knifes for 8 dex damage per round. There's really nothing you can do except cast Remove Resistance (which allows a fort save) to get through his resistance with any dependability.
But give it your best shot.
Are you sure you can't talk the DM into letting you Planar Bind a Planetar who will Gate a Solar for you?