The Black Book was definitely a weekly publication, certainly from the mid-seventies onwards. It's what got me into racing. My dad used to buy Timeform cards from a newsagents on Arundel Gate in Sheffield - and they did give him an edge, although he was too indisciplined in his approach to betting to make the most of it - but they were quite pricey and he got better value if he bought a Black Book and paid his teenage son a bit of pocket money to go through all the cards and work out the weight-adjusted ratings. Said teenage son gradually started betting himself on the apparent "good things" and the rest is history...
Yep they were posted on the Thursday of each week. I found half a dozen issues purchased at strategic points in the season ample data to work on. The ratings were unadjusted (i.e. different to the age- and weight-adjusted ratings in the Timeform race cards). To adjust for race card ratings the procedure of adding or subtracting points for pounds below/above 10 stone, had to be undertaken (as you point out). During the course of the season the figures rose to several pounds higher than were recorded in the TF Annuals where the ratings were subject to a re-handicap in the winter, where they would return to the standard level from which the definitive Timeform Rating in the Annuals were derived. So throughout the season ratings for the best horses could rise to above 140 but appear in the low to mid 130s for the Annual.