Russia first needs to get a better port than Okhotsk (and those other ports along the stretch of coast). Thanks to some nice treaties with China, they finally got those nice ports.
Contrary to popular belief, Alaska is actually a decent place for agriculture, although not heavily profitable agriculture. Unfortunately, the mid-19th century is when Russian peasants first started growing potatoes (probably Alaska's best crop besides exotic crops like quinoa) on a wide scale. But there's still agriculture to be had.
Yeah, but the existence of Alaska and presumably building tensions between the US and Russia over American citizens there could cause a change in alliances. Will the US start the war? I doubt it, but say Japan and Russia are at war, another incident happens with American miners and the Russians in charge, what's America to do? Not that America won't have a large faction against another imperialist adventure, this one against a country far worse than Spain.
We're working with different relations between Britain, the US, Japan, and Russia compared to OTL thanks to the existence of a successful Russian Alaska.