About the backspace protection: What browser are you using? I tested it using both Firefox and Chrome, and even though it didn't ask me to confirm that I wanted to leave the page, I was able to click on a link away from an unfinished message, then hit the backspace have my message still be there in both browsers. Maybe I'm misunderstanding your problem, but the only times I've ever lost messages here were when I accidentally closed the entire browser somehow (if I just close the tab, which happens a lot more frequently, the text is still there when I recover the tab). In fact, I've clicked links away from this message several times while I've been writing it as a test, and haven't lost anything.
As for your language question, I don't understand the first option at all; do you mean write out the Russian phonetically in Roman script as opposed to Cyrillic, or write English that's directly translated from Russian with no effort to change idioms or grammatical construction, or something else altogether? And, for that matter, does the second option mean the Russian would be written in Cyrillic? Actually, it's not particularly important, because my answer is the third option in any case. You can't really write a novel with significant portions in another language, because even if you provide translations in, say, a footnote, it's very distracting and annoying to the people who don't speak the second language, which, especially with a language like Russian, will likely be the minority. After all, you can't subtitle a novel. What I'd probably do is just establish somehow that when characters speak Russian, the dialogue is written in italics or something similar to that (what I would do is write out a line in italics, make a reference in the narration to the fact that it was in Russian and not English the first time this happens, and then from that point on, and let the reader assume all italic dialogue is in Russian).
Even though there will undoubtedly be some readers who do speak Russian as well as English, it's generally best to assume when writing that your readers only speak English or at least don't speak Russian (or whatever the language in question is). The ability to enjoy a novel should not depend on previous knowledge of a specific second language in addition to the main language of the narration.
I hope that helps!