We can't know which bangs Mrs vdm heard. Mr Johnson may well have been woken by the first bangs. Otherwise he was woken by screams which failed the wake the near neighbours who apparently slept through all the very loud screaming.
If Op hadn't said the sequence of events in the bail affidavit, I'd agree they were using the evidence to construct some story. But he gave it before they had the evidence, certainly before they had berger and Johnson evidence, which in the end corroborated his version in terms of times of phone calls and screams for help.
bib - this doesn't prove anything. so their house is on a different sound path or they had their windows shut or they're heavier sleepers or their hearing isn't so good. You can't rule out witnesses who did hear what was happening because others weren't woken.