Treecats are sentient aliens, not pets.
They are (more or less) symbiotically bound to their humans; if the human dies, they usually die of depression. Exceptions are rare and significant.
Treecats on starships are supposed to appear out of place: they are resented by many/most(?) crewmembers, who see them as pets.
As for Grayson: the planet is strategically important in the Havenite Wars and no society caught in such a conflict can avoid getting caught in it. They are the product of their history and environment. Which latter volumes slowly reveal. Judging them by present culture and mores is to miss some of the elements Weber is playing with.
Honor of the Queen is a cornerstone of the series, not a casual throwaway.
As for the series itself, it is structured as three phases, so far.
The first six volumes cover the rise of Honor Harrington from merely a promising naval officer to a prominent political figure at the galactic level.
The next six or so cover her roles in the Havenite Wars and eventually the series expands beyond her to focus more on the broader (and deeper) conflicts at play.
It is only late in the series that the broader background hinted at in the early volumes (like the amount of traction and support Haven gets from the Solarian League from the beginning) come to the foreground.
Certain aspects of the background are clearly latter additions and enhancements but most of the latter developments are at least subtly hinted at from the beginning.
The series starts out as straight SF military action but the series over time expands its scope and becomes a ringside view of an Epochal War at a galactic level. Which is a bit more demanding but also rewarding.
And no, the series is not likely close to ending.