1) Yes. There are bus services from Staines station that go to Thorpe, so you should be fine with that. Otherwise the park is about an hour's walk away (so I hear).
2) The park is often pretty busy during the summer on days the weather is good, so expect long queues in places if that's the case...especially for water rides.
3) I remember when the Shark hotel was The Crash Pad in 2013, things like stand up comedy was available, so I expect this is one of them. Fin's Bar and Grill (what was Bar 360) and the Coffee Shack will also be open.
4) Like Alton Towers and Chessington, hotel guests are allowed in the park a whole hour before the park opens to everyone else.
5) I think the rides shut for both hotel guests and the rest of the public at their designated closing times, hence why evening entertainment is provided within the Dome.
Hope these help.