I-140 is already approved and shouldn't be impacted by the L-1A Extension's denial.

If your spouse is in the United States then you can file the I-485 with the I-130 receipt notice. If your spouse is outside of the United States,...

There is no need to wait for the I-797 to be corrected. A new employer can file a new H-1B petition which will update your name on your I-797.

Yes, since the visa is current and you are in F-1 status you can use it to enter the United States.