Answer to you second question:
after you run the report, right click on the column heading and select "EDIT HEADING" you can enter you custom name here.
the worksheet sql is always structured according to the EUL (end user layer) . if you have used two clients tables and created a join to different tables then the sql will be generated as per your requirement . there is no way we can have Discoverer create a sql like that . if you are so interested with the sql . you can create a custom folder in the business area and paste the sql and create a report on top of the custom folder .
you can always edit the heading in the discoverer plus workbooks as per your requriement
hope this helps