About the garbage truck…
You understand, I take it, that Max (James Woods) faked his own death years ago, and that while David/“Noodles” (Robert DeNiro) spent decades mourning for him needlessly, Max had assumed the name Bailey, and had become extremely rich and successful. Indeed, Max had made it to a Presidential Cabinet level position.
But Max’s past and his corruption caught up with him. He was about to be indicted for corruption and for Mob dealings. He also knew that the Mob would surely have him rubbed out soon, to prevent him from testifying against him. So, tired of waiting to be executed by the Mob, Max called his old friend Noodles. He hoped Noodles would take the opportunity for revenge and kill him.
But too much time has elapsed. Noodles isn’t the same angry young thug he once was. He doesn’t want to kill Max- he doesn’t even acknowledge completely that “Bailey” is Max. Noodles is just a tired old man now, and wants to go home. He leaves Max’s house via that secret passage.
As Noodles leaves the house, we briefly see a human figure come out of the house behind him. I THINK it’s supposed to be Max. And I THINK Max committed suicide by jumping into the back of the garbage truck.