What is the distribution of daily hours for Western (e.g. Benedictine) monks?
The reason that you can not find any real references to this question is that there are too many variables to be taken into account.
There are 19 Benedictine Congregations within the Benedictine Confederation, plus six monasteries directly subject to Rome. Even in the Middle Ages times varied between these houses of religious traditions. This is not including other monastic orders like the Carthusians.
Even on what you call normal days will vary even within the same religious house of formation. Fast days will be different than non-fast days. The evening meals might take 45 minutes to finish; whereas evening collation may take only 20 minutes. Some communities (most) have communal recreation times, but not all. Even this is a variable between 1/2 hour to 2 hours a day.
Another variable would be in how traditional a particular community is. Traditional houses will still say the complete Divine Office composing of Matins, Lauds, Prime, Terce, Sext, None, Veers and concluded with Complines all chanted in Latin. Most communities now have suppressed Prime altogether. Many have now combined Terce and Sext as a form of Midday Prayer.
Another variable is in the fact that in more modern communities there is only one concelabrated convenual mass; whereas in traditional houses monks will say low masses privately and then chant the main mass later that morning by the weekly priest hebdomadarian.
Thus traditional communities and non-traditional communities would sleep approximately 6 hours. Some monasteries I know get more than six hours.
Let us look at Dom Delatte’s Commentary on the Rule of St. Benedict
We should remember and practise the instruction : "When the signal is given . . . rise without delay." We must not rise piecemeal, bit by bit, but immediately and as it were mechanically: it is easiest in th<* end. The Divine Office, both the work and our disposition towards it, will suffer from the unhappy self-indulgence and petty calculation which give us an additional twenty minutes of sleep every morning. Eight hours of sleep is more than was granted by old rules of health:
Sex horas dormisse sat est, pueroque senique; Da septem pigro: nulli concesseris octo.
As for prayer, traditional houses will have close to 7 hours, while more modern communities will have around 6 hours of prayer. These times vary great even within the same Congregation of Benedictine monks.
Based on personal experience I would conclude that the average times would be as follows:
Work: 4 to 7 hours depending on work, studies and other necessities. Lay brothers would definitely do more. Yes Lay Brothers still exist especially in more traditional foundations.
Prayer: 5 to 7 hours depending on how traditional or modern a community is.
Reading: 1/2 hour to 1 hour spiritual reading per day.
Meals: 1.5 hours (less on fast days). There are still communities that fast the entire season Lent and old fast time of the historical ways prior to Vatican II. (Carthusian have a communal meal on Sundays at noon only.)
Recreational time: 1/2 hour to 2 hours where this practice is in usage. This is across the board for both traditional communities and more liberal ones. (Carthusian monks do not have daily recreation.)
Community lectures by superiors: Vary from from 1 hour (some Benedictine Abbeys) per week to 1/2 to 1 hour per day (some Trappist monasteries).