If you read the act, Congress can declare that emergency over by passing a joint resolution. If Trump declares such an emergency, Congress can quickly end it. If one House of Congress passes a resolution to end it, the other house is required to send it to committee and within 15 days report it to the floor where it becomes the order of business which means leadership can't prevent a vote. It looks like the maximum time frame for Congress to act to overturn any emergency declaration is 36 days from the first introduction of such a resolution. Every member of Congress is going to be on record before it ever makes it to the courts. I don't see a majority being willing to agree it is a national emergency if they hope to be reelected.
Yup. Hence the reason I stated they passed the act. To gain some control and to set an expiration. At the time one of the emergency acts from Roosevelt in 1933 was still in effect, there was no expiration, until 1976.