you have several issues here :
1. BIlaunchpad/web session timeout issue
2. CMC enterprise sessions issue
3. Webi reports long refresh time
4. DB queries not terminating.
Start from #4 and move your way up.
Why is the queries do not terminate in oracle? (question for your DBA, unless Webi actively uses connection and data is exchanged, its Oracle's responsibility to recycle idle connections)
How is the DB connection setup in universe ?
Why are these reports refresh so long ? (better design maybe needed ?)
etc...