One thing I've noticed is that "He reads" and "He is reading" seem to be both он читает.
Is there such thing as a present participle in Russian, or some kind of approximation to distinguish between the concept that someone does something sometimes vs that they are doing it right now?
"He reads" (without further context) means that it's an activity that he sometimes does.
"He is reading" means that right now, reading is the activity he is involved in.
Is there just no distinction in Russian and you have to determine it from context?
There are present (as well as past) participles, but they are not used to form continuous tenses.
Even "He has been reading" is part of читает (Present perfect continuous) But "he has read" is part of the past (Present perfect) Russian present tense just cares about actions that are still on going.