Pathetic. All I see you say, time after time, is that "evidence places Oswald in the SN at 12:30" (which is an outright lie as there is no such evidence) and "nothing precludes Oswald from being the assassin and being in the 2nd floor lunchroom" which is also a lie.
What I don't see you do, in fact what I never see you do, is support your silly "could have" claims with anything that actually shows that Oswald was the assassin, that he was in the SN at 12:30, and that he managed to go down the stairs in 75 seconds or less after the shots without being seen or heard by anybody.
The notion that the presence of a rifle (even if it was Oswald's, which is doubtful) and three shells somehow proves that Oswald was on the 6th floor at 12:30 is simply idiotic.
You know the evidence that places Oswald in the SN (i.e. his rifle, fired bullet casings from his rifle, his prints on the SN boxes, his prints on the bag, no credible alibi, flight from the scene, involvement in another murder less than an hour later, lying to the police about his ownership of any rifle or explanation for its presence in the building). We also know from several witnesses that a rifle was pointed out the 6th floor window at the moment of the assassination putting someone in the SN at 12:30. We also know that Oswald was encountered on the 2nd floor sometime shortly after the shooting. Your insistence that it was 75 seconds is your subjective estimate. It could have been less time or more time. There is insufficient information to track Oswald's movements and those of others down to the level of detail that you insist is accurate. Just a short variation changes the whole equation and allows Oswald to make it to the 2nd floor unseen. There is no reason or basis to debate the unknowable while ignoring the actual evidence that tells us where Oswald was at a particular time.
Your explanation for all the evidence left on the 6th floor and escape of whomever you believe was in the SN is preposterous and baseless to the point of being humorous. Your desperate clinging to some pedantic timeline that you have constructed to suit your desired outcome is identical to your bizarre approach to Oswald's involvement in the murder of Tippit. You attempt to construct a timeline from imprecise witness estimates to prove he couldn't be there when multiple witnesses place him at the time and place of the shooting with the gun in his hand. It's Alice-in-Wonderland logic to suggest that you can conjure up a timeline by somehow knowing not just to the minute but often within a few seconds that some action took place when the participants themselves didn't have this level of knowledge and were merely making estimates. And then claim over and over that this casts doubt on the actual evidence. The evidence speaks for itself. It places Oswald in the SN at 12:30 and then in the lunchroom whenever the Baker encounter took place. Of course, if someone HAD seen Oswald coming down the stairs, you would dismiss that with some contrarian explanation like he worked in building, or it doesn't prove that he was on the 6th floor just because he was seen on the stairs etc. An endless impossible standard of proof.