Hi,
1. If you are using EHP 5 or higher yes there are differnt ways to debug WDA especially designed for WDA.
2. For performance...its just the conventional way, however there is some better tools recommended/developed by SAP AG.
http://www.sdn.sap.com/irj/scn/index?rid=/webcontent/uuid/50ea87c7-e355-2d10-caba-cb6c7e54671a
3. Passing parameters : mentioned above
4. Stateful/Stateless : - WDA is stateful as there is nothing being done at client end. intitally there were possibilities to use javascripting and all in WDA. However due to security constraint, SAO do not recomend using such things. So what it does is almost every calculation in backend, Hence its stateful. You can browse though for more details
5. The only way is I know is mentioned above. Do some RnD its possible that you may find all new fancy details
Vishal
HAPPY ABAPing
