The sound of the wood sections being broken would be loud and possibly are the source of the third set of sounds. Wood makes a very loud "CRACK" sound when it is broken. And the entire upper section of that door was torn out in pieces.
Regarding <modsnip> and testimony that the bullets hit the door before the bat hit the door. He was testifying to "when the bat was used to pry loose the first thin panel." That is one of two separate events related to the bat. And he was correct that the bat came after the one bullet hole because the tear went through that one bullet hole. However, he said it was not scientifically possible to conclude which came first, the two minor bat strikes or the 4 bullets. So two events are distinguished with the bat, first the two strikes to scare Reeva and second the bat being used to pry the thin panel section loose.
I believe that the following is correct:
1) The bat was struck on the door twice to scare Reeva and it was used to strike the bathtub plate very hard - first set of noises
2) The gun fired 4 bullets in to the door - second set of noises
3) The bat was used to pry to slender panel piece loose and then OP took to breaking all of the upper panels of the door - creating loud cracking sounds as he broke them off of the door.
The first three witnesses don't agree with you. They all heard woman screaming [and man] and then 4 gunshots at 3am, after which the woman screamed no more.