Hi Tiago,
Let's see if I can answer all your questions.
1 - Not showing the Guest number is because you forgot to do an ajax refresh on OnRoom_RoomNumberChange when the room is valid. you also need to set "IsValidRoom" to true.
2 - Wrong value on check out. on GetRoomsWithBookings you need to sum the RoomService.Amount and booking should be with or without room service because not all the rooms will have room service
3 - on the delete error. you need to check if the booking has room service. if yes you can't delete it.
in attachment I your module with some changes.
Regards,
Marcelo