After you file

To follow-up on the comments form @DaveD66:

Question No. 1 - Still use your spouse's current name.  

Question No. 2 -  The standard deduction amount could be the reason for the changes you are seeing.  The 2018 standard deduction for MFJ was $24,000 and for MFS the standard deduction was $12,000.  Those amounts are adjusted if the taxpayers are 65 or older.  You may want to provide some additional information regarding the specific numbers.  

Question No. 3 - Assemble any schedules and forms behind Form 1040-X in the order of the “Attachment Sequence No.” shown in the upper-right corner of the schedule or form.  If you have supporting statements, arrange them in the same order as the schedules or forms they support and attach them last.  Don’t attach a copy of your original return, correspondence, or other items unless required to do so.  Attach to the front of Form 1040-X:

•  A copy of any Form W-2, Form W-2c, or Form 2439, Notice to Shareholder of Undistributed Long-Term Capital Gains, that supports changes made on this return.

You can staple your W-2 to the Form 1040-X, but you can use a paper clip or similar clip to hold the bulk of the documents together.  No need to staple all of the documents together as the IRS will likely want to separate them.   Not sure if certified mail will work as someone probably needs to sign the return receipt and if there is no one present to sign, you don't want the certified mailing returned to you.   You may be able to designate that no return receipt is required, and then the certified mailing will work just as well as a standard mailing.  In either case, keep a copy of your documents including the post office receipt for the postage.  

@JohnB_303