To change the summary you need to access the report definition.
You will need the Premium version to do this and you need to create a new definition and report based on the stock one, go into fields, click on the AWT field and then click edit formatting and in there change the footer from SUM to AVG.
To summarise by day is a custom report too and will involve writing the sql to do it as I don't think theres a Daily Summary template out of the box,
You are correct on the steps on editing the format for the footer. However i think you can't do an average of an 'Avearage Wait time', though its technically possible. It needs to have a custom formulae. I believe i posted the formulae before, not eactly for AWT but you will get the idea here.
http://developer.cisco.com/web/ccr/forums/-/message_boards/view_message/5202487
As for the second question, you need to modify the query to remove the EntName, CallType from Select, GroupBy and OrderBy. Check here,
http://developer.cisco.com/web/ccr/forums/-/message_boards/view_message/5192315
If this is for Caltype21 with summaries (instead of 30 min interval). I can get my report.
-Senthil