Approach 2: use a fantasy setting for a science fiction novel.
How does it address problem 1? Obvious. My characters can be ordinary humans, and I can bring them to life using the common tools writers use to characterize the protagonists and their surroundings: appearance, clothing, gestures, descriptions of nature, architecture, etc. A bonus: I can use fantasy cliches -- in a good way, as shorthand. (The Fantasy Cliches panel in this year's World Fantasy Convention validated my temptation to use this approach. :-))
How does it address problem 3? Well, a fantasy world can be anything I want it to be, and it does not have to correspond to any real-life setting with which my readers may be familiar, so there is no requirement of accuracy. Thus, I don't have to imitate a cowboy dialect, or street slang, or British upper class speech mannerisms, or any of those things I'm completely ignorant of.
How does it address problem 2, the problem of introducing unusual ideas and explaining them without slowing down the action? Perhaps it doesn't; it's just that at least a fantasy setting doesn't work against it, because cliches-as-shorthand can move the story along to counteract the slowdown caused by explanation. The trickiness of this appraoch is, of course, how to reconcile science-fictional ideas with a fantasy setting. Advanced scientific ideas can't spring out of nowhere in a non-technological society. Well, there is an old cop-out: the science in question was introduced by an advanced technological civilization that long ago had visited the world where the action takes place, and left its artifacts, or perhaps passed some of its knowledge to a special caste of priests or wizards. It's an old, hackneyed setup, but I'm not going to reject it just because of that. The editors on the Fantasy Cliches panel swore up and down that cliches are OK if the story is good. They also said 90% of attempts to completely avoid cliches lead to a dull story without a plot. Who am I to argue? :-)
I already have some ideas for a story or, hopefully, a series of stories, that will use Approach 2. Of course, I can't use this approach in each and every story I write (unless it's a series of connected stories), or it will get old very soon. Still, now that I've thought of two ways to navigate around my roadblocks, it gives me something to do. For the next couple of years, even. :-) If I successfully implement both, I'll be in good shape. Then I'll have to worry about what to do next, but perhaps by then I will have built stronger writerly muscles and will have acquired a bigger arsenal of tools.
Though it's not easy to feel too optimistic about it at the moment.