I think that the overdue bills may very well not indicate financial hardship as much as establish the trope of the "absent minded professor"... So focused on the genius of inventing that he forgets mundane things like paying bills and housecleaning...

The DeLorean, for all intents and purposes... exists outside of time. Young Biff barely had the book in his hands before Old Biff was back into the future where changes hadn't been made yet. Most time travel requires us not to think of time as a linear moving wave, but rather an infinite number of moments happening one right after another... like a movie made of separate frames each slightly different from the other but when run together rapidly enough appear to have fluid motion... as such, it takes a while for these infinite points on the timeline to update and change one after the other to form a changed timeline... much the same as the gradual loss of Marty's older siblings in the photo as his disruption of the past made his own parents meeting and falling in love less and less likely. Alternately, there is the theory that our timeline is already set, but a person moving outside of time from a future point, stops existing in that future point moving forward... but instead starts interacting with the old timeline creating a divergence and new timeline both exist independent of each other, in an infinite number of possible timelines that we generally only perceive one of at any given time... the one we occupy. To us, the one we're in IS the only real one. To answer your question in THAT theory, the book doesn't disappear because it is from another timeline that Young Biff and the rest of the world stopped living in once he got the book and started using it.

The ripple effects on the timelines reflect how directly affecting deviations are to the timeline in general. In the first Back to the Future, Marty's siblings and even Marty himself began disappearing from the photo because Marty's arrival disrupted George and Lorraine's first meeting (Marty's parents)... without that meeting, they don't fall in love and Marty and his older siblings are never born... the timeline slowly solidifies its effects as their falling in love becomes less and less likely, manifesting by each sibling disappearing in order of birth until Marty's continued intervention results in them falling in love as before... though with the unintended bonus of increasing George's self confidence and life path with Lorraine. The ripples seemed very pronounced because we saw the 5 people directly affected in real time. However, Biff using a sports almanac from the future would likely have very little effect upon future sports... Sports betting currently is $150 billion industry. You can imagine that single person betting on multiple sports could amass tems of millions of dollars without having any substantial effect on sports in general... as money won or lost has little direct effect on the players and games moving forward. Certainly, if Biff became too greedy betting too much on single bets or ONLY made winning bets... he'd likely be investigated, or make some powerful enemies... but with strategic betting, and believable loss bets mixed in... he'd just become one of the best odds makers and career gamblers, but not raise too much interest. Maybe the occasional high odds three horse parley for a big payday... but pretty discreet of how many times he bucked the odds and won. He could also bet on things like points spreads without obvious inside info.