Don't forget a couple things.
1) Bloor station was updated 10/15 years ago - I forgot exactly - and this vastly improved the flow at the station. This accounts for the less congested feel now compared to 20 years ago.
2) You're probably right about peek ridership - considering the when the employment was highest in Toronto / core it makes sense that it could be have busier before. I do wonder what the frequencies were back then though.
3) My view is off peek ridership on everything (buses, subways) is a lot higher then the past!
If I had a penny for every time someone asked me why I was looking upů