What did Hoover have to work with?
Oswald ordered a Carcano rifle.
No, unscientific and biased handwriting "analysis" of 2 block letters on a photo of a microfilm copy of a 2-inch order coupon said that Oswald ordered a similar, but not identical, rifle.
Oswald holding a Carcano rifle.
There's nothing uniquely identifying this as a Carcano, much less a particular Carcano.
Oswald's carcano rifle on the 6th floor.
Based on a previously flawed assumptiom
Oswald's shirt fibers on Carcano rifle.
No. Similar fibers that can't be uniquely connected to any particular shirt.
Oswald has no alibi.
As do at least 6 other people in the TSBD alone.
Oswald's killing a Police Officer.
Oswald's trying to kill more Police Officers.
Both claims assume facts not in evidence.
And you reckon there was a reason to doubt that Oswald was the real assassin?
Yes. When you have to misrepresent the evidence to make your argument then you have no argument. Even if you could prove that Oswald ever possessed this particular rifle (and you can't), that doesn't prove that he shot JFK with it.