I have to agree that the Goldfish do not mix well with the tropical fish.
Yes goldfish will eat the cories if they can.
And i agree with Zagz in saying that the only fish in that tank that it is ok to have that much salt in the water is the mollie. Mollies can handle a lot of salt and are classified as brackish water fish. But they can thrive great in FW
(no salt in tank). I have 2 mollies and a bunch of mollie fry in my 10g (which has no salt) with 2 ottos and alll the fish do fine
If i was to give you advice then i would say get the gold fish a new tank and SLOWLY decrease the amount of salt in your tank by doing PWCs put FW
(water with no salt) in tank. And keep doing this over time until you no longer have any salt in your tank. Dont do any major changes though as the decrease in salt might be too large that the fish may be stressed. Then after the water is all fresh and the goldfish are gone then i would go get a nice school of cories