If you're not tied to Excel, Access can automatically build an event management db for you with the type of reports I think that you are looking for.

If you are tied to Excel, attached is a spreadsheet that is an example of what it sounds like you are trying to do.

Enter the attendees on the data sheet and flag yes to any day they are attending. Then navigate to the sheet. Turn off auto filtering if its turned on then sort the list and reapply the autofilter for non-blanks. This should give you a list for just that day.

It is ugly. A better solution would use Excel VBA or Access as mentioned previously.

To your second question, you have formatted two or more cells as merged. Sorting will not work across merged cells. Change the cell format or don't sort the merged cells.