Below are the weekly Nielsen ratings results for the 1972-73 television season. Viewership wasn't reported by Nielsen until the fall 1988 season, so up until that point the only metric widely available was the household rating (which is what is reported here in this article). To calculate the estimated number of households watching, just multiply each rating by 648,000 as that is what 1 rating point represents.
This season was an oddity in terms of ratings because it was the first season where full ratings were released for nearly every single week. Beginning with the week ending Oct. 8, 1972, The Los Angeles published both the full weekly rankings & ratings and they did this up until the week ending April 8, 1973. For the first week of the season (w/e Sept. 17, 1972) the full rankings are available from Broadcasting Magazine and the top 20 ratings are available from The Boston Globe. For the next 2 weeks of the season (Sept. 24 & Oct. 1, 1972), the full rankings and top 15 ratings are available from Broadcasting Magazine. The summer season is basically only reruns so it's not worth my time to try to dig up info for those 5 months.
Note: the week ending Dec. 31, 1972 was a Nielsen black week so there is no ratings information available that week. Additionally, The LA Times did not publish a list for the week ending March 25, 1973 so I had to use a number of other sources to compile as much of the rankings as I could. There is hardly any ratings data available for that week, but about half of the rankings are there.
ARCHIVED WEEKS (w/e Sept. 17, 1972 - Apr. 8, 1973)
Source: Nielsen Media Research via The Los Angeles Times, Broadcasting Magazine, The Boston Globe