Scan the group a bit, there has been some who has been asked to provide more information (might be depending on where the visa was acquired). But normally you're only supposed to need what you entered on the first time: the visa printed out and your passport.
Anonymous participant well, you have your answer there. Use your METV until it's expired and then apply for DTV. You cannot habe two visas at the same time.
If your DTV is denied, you can try to apply for a new METV or try to enter Thailand on visa exemption.
When exiting Thailand, your current visa or visa exemption will be canceled. Be sure to do so before the 60 day stamp expires. When entering next time, you will show the DTV and get a 180 day stamp.
The stamp is not the visa. A visa is an allowance to enter the country. The stamp says when you have to leave.
No, it's likely going to be denied. Unfortunately they're very very strict when it comes to dates and names matching 100 % with the passport information. The site really tells you to double check the data before submitting.