His wife was 10 when he married her?

Not uncommon at the time. It was how it was, before. Try to read up on a little bit of world cultures and history. In India, most of the time, the girl would either go back to their own family after the wedding, and be sent to her husband's family after she reached puberty, or be living with her husband's parents. i.e., no real sexual contact would occur until much later.

My grandmother was married when she was 14 (in 1922) and my father - her first child -- was born in 1926. My grandfather was 12 years older than she was.

My mother is 12 years younger than my father. Hey, I wouldn't go for that sort of an age difference myself, but I'm not a product of THAT era.

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Fear not for the future; weep not for the past -- Percy Bysshe Shelley
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Such marriages were actually betrothals.

For facts about Ramanujan's wife see this short paper from The Institute of Mathematical Sciences in Chennai (http://www.imsc.res.in/~rao/ramanujan/newnow/janaki.pdf). One Indian documentary on YouTube says Janaki was 9 when they married, but 10 does seem to be correct. Ramanujan was 21. Apparently child brides were the custom at the time. Perhaps such marriages were not immediately consummated. Not long after the wedding she went away to live with her parents; however, she returned to live with him when she was 13, probably because she had reached puberty--no use wasting any time.

It's worth remembering that Shakespeare's Juliet "hath not seen the change of fourteen years."

So the movie completely lies about the age of Ramanujan's wife, portraying her as a beautiful, fully mature woman, pumping out all the usual movie clichées--they run through the surf, drawn together by a mutual passion, etc. Total nonsense. I understand that to portray the truth and make it somewhat palatable to modern audiences would take far too much screen time. But I'm not quite sure why they had to give his marriage and their "love" such prominence in the story, since it required an unfortunate amount of dishonesty. A simple matter of trying to inject a little romantic interest into the story, I suppose.

it's just a question of cultural norms for the time location - for one thing, not many people fail to live to be older than 32 these days - life expectancy in India was perhaps 50(?) at that time.

You cannot apply today's standards to the past, and claim it was "weird" or unnatural. Even in the US, not too long before the events in the movie, the age of consent in some places was as low as 10 years old. It wasn't until the early 20th century that it was raised to 16.

And at the time, many cultures married girls at a young age. But, they didn't consummate the marriage until puberty. The movie doesn't really get into that (there would be a lot of criticism if it did), but when it starts with them being married and later moves to be with him, along with his mother. And when she first moves in with him, he sleeps on the floor instead of with her in the bed until much later. Again, the movie doesn't specify her age, but he leaves for England in 1914, which would put her at about 15 at the time. So by the time he actually sleeps in the same bed (and if we induce sexual activities around that same time), she very likely would have reached puberty.

Usually they get pregnant immediately. But they had no children in this movie.