Yep, I think I can work with you on the time in jump. My CT universe has always been a week in space (jump and normal) in usual circumstances. It only takes about 8 hours at most to transit to or from 100d of a world and is included in that one week travel time in the simple method. Fits your 150 hours flat quite nicely.
In a more complete accounting of time you might shave off enough hours and minutes over the course of a year to gain a couple days, or more with a fast (high G) ship, over the course of a year.
When was the variable time in jump space introduced? MT?
In any case, even then my take on it was not that the time was unknown or random, just that it varied for the jump and the trip to and from 100d depending on the actual distances. And you always knew precisely how long jump should take, and precisely where you should come out. It was only in the case of a misjump that all those numbers went out the airlock, and sometimes the first clue that anything was wrong was when the ship didn't drop out of jump space at the appropriate time.