Those things you list as "very strict" are incredibly easy. And they do not make any difference to the US regarding domestic violence.
The end result is a small minority having multiple guns per person, the majority not having any, so citing Finland as a country with high gun ownership is misleading.
About gun ownership in Finland, Wiki tells me:
> There are approximately 1.5 million registered small firearms in the country. Out of those, 226,000 are short firearms (pistols, revolvers) with the rest being long firearms (rifles, shotguns). There are approximately 650,000 people with at least one permit, which means 12% of Finns own a firearm.