The increase in the size of the House in decades before 1920 was driven by political considerations, not merely population increase. The best approximation to the politics going forward from 1920 would be to set the total number of reps at each apportionment to the minimum number such that no state loses seats in the coming decade.
I ran an analysis to see what would have happened if this rule (actually the version where you said a state could only lose representation if it lost population, and otherwise no state that gained population could lose representation) had been in place from the founding of the country. It was interesting. I haven't really grappled with what it would have meant for the electoral college results (but I'm sure it would be like you've detailed here), but we'd have 4,473 representatives today, with no state having fewer than 8 representatives.
