Would Diane and Hollyhock be in his life still?
i don’t know about the other questions you asked, but these two i think would still have left his life, since their primary motivators for leaving him revolved around penny. not that the sarah lynn story didn’t play a part (particularly for diane), but i don’t think that not coming to the surface would have changed the end for these two characters in particular.
no. herb made it very clear that what he could never forgive bojack for was that he abandoned him as a friend when he needed a friend most. reaching out sooner rather than later wouldn’t change that fact.