Unreported, yet you claim to know the true number. By magic? Or just made up to support an agenda. I think its the latter.
Based, on facts, if you'd bothered to check for yourself.
"on average there will have been 35 assaults before a victim calls the police" - so yes, vastly under-reported.
What I am suggesting is letting people know if their partner has a history of violent crime (something that in some circumstances they can already check for themselves, but I believe it needs to be more proactive).
As for the police beating people up, do you have any sources for that, or did you invent it to suit an agenda? It might have been a historical problem, but these days, with CCTV in police stations, and almost everything being referred to the IPCC, I think you'll find that it's a very small problem, compared to domestic violence.
My partner happens to work with victims of crime, a large number of whom are victims of domestic abuse, so I happen to have some inkling of what I'm talking about. Unlike you, it seems.