Norway inflation and exchange rates
I do not know Norway's economy. BTW, based on what you report, I would first rearrange your points into a more chrono-econo-logical order. Briefly,

3 - Facing the loss of income due to the massive drop in the crude oil price, --
depending on the impacts that this drop may have in term of income redistribution -- Norway's economic agents may have increased their saving rates $\iff$ economic agents consume less. Less demands means weaker upward pressure on prices, which in turn means less inflation.

1 - Facing the increasing masses of savings, Norway's central bank may have started to decrease the interest rate so as to disincentive agents to do so. Indeed, lower interest rates $\iff$ lower rates of return on savings -- if commercial banks propagate this rate change, which is very likely. 

2 - Finally, since these lower interest rates tend to attract less foreign investments -- and since, to access to Norway's lending market, those must first buy home country's currency -- this exerts a downward pressure on the value of Norway's currency, which in turn causes a relative price increase of imported goods $\iff$ imported inflation.

To conclude, I would say that your points 1 and 2 are as correct as they are incomplete.