Could Russia adopt the Tlingit as a client state?
Did they every encounter anyone so advanced in OTL?
Probably not; I don't know *all* of the details of the Russian conquest of Siberia and the people they conquered, but I think the Tlingit were the most-advanced folks they ran into OTL.
Thinking about it I have another question, will the Russian government decide to take any colony under direct administration instead of leaving it to the fur company?
Great question. Russia is going to be a pretty different place OTL; the very different New World will have pretty significant effects on the Old World, and by the time the Russians make it to Alaska there will be about 300 years worth of alternate European history behind them. I'm still sussing out the details, but it's fairly clear to me that Russia will be a more eastward-looking, Asian-flavored, but centrally controlled state ATL. So I would guess, yes, Russian colonies, only because the idea of a chartered but private commercial company, which is what the RAC was OTL, would be somewhat alien to Russian mindsets in this universe.
The *most* intriguing possibility, I think, is a completely stateless Russian entrance; with a less-technologically advanced Russia, the fur-traders and Cossacks in the Russian Far East might just end up crossing the Straits of their own accord, without the Czars having ordered it or even knowing about it. They will definitely be able to overwhelm Sugpiaq [who became Aleuts OTL], Inupiat, and Yup'ik peoples ATL, with disease if nothing else...but I'm not convinced that without Russian state sponsorship they can handle the Tlingits. What they *will* do is creolize the Natives all over the place--like the French and unlike the English, Russians in the New World enthusiastically married Native women and adapted Native habits, if not their religious beliefs. So there's a real chance that the Russian-Native creole people will just be one of a number of native groups in Alaska... and not necessarily the most powerful one!
It'll probably be a bit before I post a new installment. I will either tell the tale of the alternate history of the Russian conquest of Siberia and movement into North America; or, I'll take a look at the Inupiat ATL (probably with side notes on Athabaskans and Yup'ik, because not much will change for them). In one case, I have to work out 300 years of European alt-history; in the other, I have to work out a millenium or so of Bronze Age New World history (East Coast BANW has been described as far north as Chesapeake Bay, but the northern Alongquins who interact with their southern cousins are going to change as a result, and eventually so will the Eskimo who interact with those Algonquins).
Lake Izok also has tin, I think you might have covered it but just in case.
I would think that ore in a lake would be beyond the technological capabilities of any native group to extract. ATL, even these more-advanced Tlingit (or the people getitng it for them) aren't *mining* for tin a la ancient Cornwall, they're picking up placer deposits--first from the Copper River, which I gather is rather poor in tin and will be worked out quickly; then from Eskimos who are pulling it from Seward Peninsula River. Bronze is a prize rarity in Tlingit society. Warriors lay very thin strips of bronze over their laminar wooden armor; only the High King and his most important vassals have actual bronze *breastplates* and weapons. Only noblewomen are allowed to possess bronze jewelry. And, needless to say, being a bronzesmith is the highest-prestige occupation a non-noble Tlingit can have, and crucibles only exist in Yakutat; bronze production is guarded as the equivalent of a state secret--as in, the other clan chiefs don't know about it--by the High Kings.