1) Name would be what you want to be referred to in the credits section of the calendar if you are to get in. I'll doublecheck this before making the credits page in case someone wants to change it though.
2) Those are two separate suggestions. All submissions need to be under 600kb, yes. The lower res image thing is just a suggestion for those who are worried about thievery (make sure the image is still clear though so people can tell what they're voting on). You're welcome to submit a 600kb image with a non-specific watermark though and ignore the lower res suggestion.