Well, to be pedantic Point A - if the bangs at 3.10 woke Stipp, then he doesn't know whether there was any screaming or yelling before then because he was asleep. So it's not really correct to say they didn't start until after that - just that that was the first he heard.
Point C: No, the gunshots were before the door was broken open. Clearly OP used the bat to do this, but they showed that he'd inserted the bat into a broken off piece and prised out the panel. All the pieces of door seemed neat - if it had caved in through almighty whacks so powerful they could be heard some distance away, then it would all have splintered - as it did when a bullet shot through.
There were a few splinters, but the pieces were intact enough that the door could be reassembled. This doesn't suggest that enormous force was used, or needed to be.
I don't think anyone heard the bat on the door that night - not loud enough and too far away. I think the noises that sounded like gunshots to everybody were probably gunshots. We know of four because we have the physical evidence. Doesn't mean these were the only ones - he was standing near an open window, and he's not been averse to shooting into the sky before, has he?
And yes, this is all supposition on my part and no, it doesn't prove anything. That's why I don't think the state can prove pre-meditation because all the physical evidence is consistent with OP's story.