I understand that you are having some issues with your Slingbox PRO since it stops working at 18.00hrs (Slingbox local time).
The Slingbox does not have any feature or capability that acts as a timer. This means that this specific issue is not related to the Slingbox per sé.
With this in mind, I recommend you to check if your router is using any kind of timer or if your ISP (Internet Service Provider) is limiting the bandwidth usage. I encourage you to contact them about this situation and let us know about their response.
Regarding your second question, you must upgrade to the Slingbox SOLO or the Slingbox PRO-HD since the legacy models (CLASSIC, TUNER, AV or Slingbox PRO) are not powerful enough to stream the iPad's higher resolution. The following link will provide you with further details about the requirements for the SlingPlayer for iPad application: