I like how Vito's tone and delivery changed after he shushed Sonny; he was truly angry in that moment and trying to keep it in for the sake of the discussion, whilst managing to get a rebuke over to Sonny. I think everyone in the room could sense the heat and so left very quietly.

I think Sonny should've been made to pay for that little indiscretion. If Vito wanted to see what Sollozzo had 'under his fingernails', he would need a prying tool, not a hammer. Luca Brasi was his hammer. Sonny just became the new prying tool.

"Since you seem to be so talkative today, I've got a job for you. I want you to go to the Tattaglias. Find out more about this Sollozzo guy, see what he's got under his fingernails. Make 'em think that I'm holding you down in the Family."

I think Sonny would've been able to play it out quite a bit better with regards to Sollozzo; it was quite clear that he was hot for the deal, so there would be precedent for Sonny to come to Sollozzo. With Luca Brasi still in play, the Don is still quite well protected, and he has the option of dropping the hammer at any time.