Nice, that’s a well realized approach. May I make a few points?
Can we avoid perpetuating this? It is simply a mistake, not a genuine alternative rendering. “So I have heard” refers to the fact that the text comes from an oral tradition. “At one time” is a new sentence, which gives the Buddha’s location.
Nice, I like it! I wouldn’t worry too much about explaining “give groups” in this context. One thing about reading is that you don’t always have to understand everything. As long as most of it is clear, the mind accepts an occasional obscure word or phrase. We put it in a “?” basket, as it were, and look for clarification at a later point. Learning new things is part of what makes reading fun, so it actually increases engagement. We just have to make sure it’s not too much.
Just in case you missed it, I’ve made a post about this earlier:
My research just used Ven Bodhi’s translations for comparison. On the other hand, I used a much larger corpus (the whole of the Anguttara 4s). Anyway, your results mostly confirm what I had done earlier. Note that the reading level for my translations is roughly the same as that for a typical (reasonably decent!) newspaper.