All you are saying is that you think that it is reasonable to hold a doubt about a piece of evidence. But reasonable doubt does not apply to pieces of evidence. It applies only to the totality of the evidence.
If every (or even most of the) pieces of purported evidence have reasonable doubt associated with them, then the totality also has reasonable doubt. Several doubtful things don’t magically combine to form an undoubtful thing.
In your Bob example, it’s not really clear how you acquired the information that you already knew about Bob. It could have been unreliable, but you haven’t given any details about inconsistencies, contradictions, or unreliable sources. You could also go to the funeral or talk to Betty to verify things. That’s similar to Aguilar talking to Odum to see if he really showed CE399 to people.