I'll give you my answers to your questions. These answers are based on little to no real data, mostly just reasoning about how Snowden's flight most likely went down, and a (reasonable, I think) assumption that he's a fairly ordinary guy, not a brilliant and nefarious planner. I also doubt that he extracted much, if any, data prior to his big grab-and-run, because it would have been too risky. So I don't think he had much time to do things between getting the dump and hightailing it.
How much additional information does Snowden have squirreled away in dead drops, that will be revealed if he is killed or imprisoned?
None. This would have required more planning, and probably more time, than is evident. Any place he might have tried to drop data in the cloud would be too risky because the NSA's tendrils are too widespread. Physical dead drops are more feasible, but they'd have to be in the US, and probably not too far from Snowden's normal stomping grounds. They'd also have to be fairly easy to locate (since he'd have to provide instructions, which he'd have to be able to remember accurately), but also well-hidden enough not to be found accidentally. That's not impossible, but it's harder than it appears, as anyone who's tried to place geocaches knows.
Of course, he could have done something like left the supposed additional, unrevealed data, or the location of the data, with an attorney or other trustworthy person. But again, the NSA has long arms, and has undoubtedly pulled out all the stops to trace his steps before he ran.
Nope, I think taking time to drop data between grabbing the dump, delivering it to the news agencies and running would have been too risky and require too much planning, so I doubt he did it.
How much information can Russian personnel gather about subtle policies of NSA, by indirect deduction of what Snowden says to press or to his handlers?
Very little that's useful. I doubt it's all that difficult for them to gather information about NSA policies, and the really valuable stuff was all turned over to the Guardian and has been published anyway.
What has, or can, the NSA do to protect its revealed policies and assets?
I doubt Snowden knows much about that. He was a SharePoint admin, remember, not an operational guy. The data he collected may contain quite a bit on that, but I strongly suspect he doesn't have that data. I certainly wouldn't have kept it on my when I took off... much safer to deliver it all to a news agency and travel without it.
What inspiration do minor details about NSA monitoring provide for Russian surveillance?
Nothing, unless the Russians are stupid, which they're not. Nothing that we've learned about the NSA's surveillance methods were at all surprising. The only surprising things were (a) the scope, (b) the fact that they weren't being careful about targeting US citizens and (c) that they were actively working to undermine security systems, in direct violation of one of their two missions. If you had asked the computer security community "Hypothetically, supposing the NSA decided to take the gloves off, ignore the law and ignore their responsibility to ensure the strength of US security technology in both public and private sectors, what would they do?", the answer you'd have gotten would have been a pretty accurate description of what they've been doing. The "what" and "how" are quite obvious.
Oh, and while I'm at it:
did the Russians use this as leverage over him to get to more information or influence him?
I don't think they could use it as leverage to get more information, because I don't think he has any more information. As for influence, well, I suppose, but what would they be influencing him to do? Just giving him a place to live accomplishes a significant goal for them, that of poking the US in the eye. I suppose they could try to convince him to strengthen their PR play, by taking Russian citizenship and denouncing the US, but I don't think they'd get anything out of that. The old USSR would have done that, and been thrilled about it, but the USSR was playing an ideological game, trying to convince the world (and themselves) that communism was superior to capitalism as an economic and social structure. Putin's Russia doesn't have that motive.