"Сейчас" is a general purpose "now". "Теперь" (pay attention to the spelling - that's how the word is pronounced as well!), on the other hand, is "now" in contrast to what was the case, or was happening before. E.g.:
Сейчас идёт дождь - It's raining now.
Теперь идёт дождь - Now it is raining (it wasn't before).
Мы сейчас опаздываем - We are running late now.
Теперь мы опаздываем - Now we are late (we weren't before).
In addition, "теперь" can be used as now in sentences like "Now, let's think" - "Теперь давайте подумаем". Since you are studying German, you will recognise this meaning of "now" as "nun" (as opposed to "jetzt").
Hm interesting, I was actually living in delusion. I thought Теперь was for general now, like "Tom lives in Russia now " , while it's actually "Now Tom lives in Russia" :-)
There you go a lingot, you kind sir ;-)
Actually here you go two lingots, I have 123 of them anyway, and you live only once ;-)
You could, but the emphasis would shift. Your sentence informs us about the timing of Tom's visit to Russia while the original sentence tells us about his current whereabouts.
You can read more about Russian word order in this excellent post: https://www.duolingo.com/comment/13955228
Tip: According to the link below, в России is pronounced like a single word