Earlier quoted context omitted.
Using that API, you could download 48,000 hacker news stories in 2 days, so if there have been less than 48,000 submissions, then what minimaxir said is true. But first you'd need to generate a list of all 48,000 story ids, and there seems to be no way to actually do that.
No need to generate all IDs beforehand. The search_by_date endpoint is fine. You have to paginate using the created_at_i parameter, not the page parameter. Also, you can set hitsPerPage = 1000. ;)
"you can only fetch the 1000 hits for this query, contact us to increase the limit"
It was a nice try, but it did seem too good to be true.