As far as what the FBI said publicly, you’d be correct they included close friends and other family in their analysis. But in a private meeting, they claimed this crime was not a “Who Done It.” And if they really thought it was perpetrated by someone outside of JB’s immediate family they would not have scorned Lanning’s opinion.
But to your original query, paranoia unnecessary. I think your perseverance is impressive and your debate skills are obvious. This is simply an opinion forum with no legal ramifications.

It is not a court of law where as a prosecutor I must prove evidence which has been stated by detectives or confirmed by experts hired by the BPD. From what Tricia posted last June, I believe it is the other way around.
“If you are going to say an intruder wrote the note guess what? You have to show us something that backs up your claim. The Ramsey forum is different than all the other forums on Websleuths.” BTW, I hate the whole handwriting discussion, for a variety of reasons which SuperDave has gone over. My understanding is that, if an IDI proponent thinks a close friend of the family wrote the note, they must prove this.
When Fides dissects JR’s story it enables RDI to experience JR working something akin to a “shell game”. Do you know, moreover, that JR changed his window story four times regarding whether he told a detective about the window being open? But an IDI here would counter that memory is fallible. That’s true. Point 1 to the IDI member. For certainly I cannot disprove that it is only memory failings which contribute to JR’s evolving statements. But is the counter argument proof and does it advance us any further in understanding JR’s mindset in changing his windows story or confuzzling his claim about calling the pilot? For me, no. IIRC past poster Meara put it very succinctly: In providing an alternate out-of-the-ordinary point, one can miss the forest for the trees.
I’m only speaking for myself here, and for anyone else who finds IDI posts compelling to answer,or to respond to with different facts, and many do, that’s cool. I’m nobody special on the forum, barely here at all.