Samantha Watson said, "You're aware that telling a FBI agent how to conduct their investigation is obstruction of justice?" It is not. Oliver is not required to allow his son to be interviewed unless a subpoena has been issued. If anything, an FBI agent in this context would threaten a subpoena rather than an obstruction of justice charge.
A photo does not need to be created with a digital camera to be printed with an ink-jet printer; it merely needs to have been converted to a digital file.