GdS story said it covers ~18m€ value Eriksen still has in our books. Don't know anything else. From that I understand insurance indeed covers that amortization, so we would get actual money from the insurance company annually, which should be around 6m€.
About the salary, FIFA/UEFA has paid his salary since he went to NT duty. I don't know when that "one year" has started, maybe when Denmark went out of the Euros? We still need to pay almost 4m€ gross of his salary this year but FIFA pays that 7.5m€ gross.
Let's hope the device can be removed and we get a new midfielder for "free".