It seems to be very hard to find any recent numbers regarding ethnicity and crime for some reason. I have not seen any numbers from your sources also, beside a newspaper article instead of the actual research, how those numbers are gathered and what they are related to.
What I can give you is my local situation, where it is very easy to find these numbers, although they are not specific to sexual assault. Those are grouped under "violent crime", which make it a bit difficult to draw conclusions for this specific situation. But it shows the following per 10.000 residents:
2013: 40 for all, 122 for people of non-Western descent.
2014: 37 for all, 113 for non-Western descent.
2015: 33 for all, 98 for non-Western descent (good drop, but still 3 times higher, just like the links posted earlier show)
Source:
CBS which would be the official statistics agency here.
Now I can't find any recent sources for Sweden, I don't know if they register the ethnicity there in official reports?
Again, I am just saying that it appears to happen more within those groups and it would be good to put specific attention to that to further drop those levels where possible.