Unfortunately, while I could point you to great books on electrical engineering in general, I don't know of a single online/book resource on this topic because I learned all of this on the job while apprenticing and contracting for many different companies. For further reading, I would probably start with semiconductor and electronics manufacturing/supply chain books of which there are dozens. If they don't cover the nuances of dealing with part variations then they are likely not worth reading. Sorry I can't be more helpful.
