Is there any reason "when" isn't a sufficient translation here for "lorsque"?
How does one say "he is reading" rather than "he reads?" I thought they were the same.
Not sure, but I think the difference is the former is sort of implying it's guaranteed that he reads 100% of the time when he's alone while the latter just implies he likes to read often when he's alone.
I don't know what you're referring to: the present simple (in French), can mean, in English, both the present continuous and the present simple.
Oh, you're probably referring to how to say in French "Whenever he is alone, he is reading." and, at least for me, those 2 questions are quite similar, with either tense. Regardless of any difference between these two in English, I'm pretty sure the sentence in French is the same nonetheless ;)
They are the same - you say "il lit" for both "he reads" and "he is reading". There is an "-ing" form in French - in this case the present participle "lisant" - but this can't be used to describe what someone is doing.
You could say "il est en train de lire" but this emphasises the ongoing activity as if is happening right at this moment.
"I like it when my daughter reads." Translation: J'aime lorsque ma fille lit.
"Whenever he's alone, he reads" is accepted. (You wrote "wherever" in your answer, not "whenever".)