On the last bit, resistance isn't a binary switch. If you assume a spectrum, then day 1 kills all the really easy bacteria. By day 4 of 8, you've killed the 85% most killable bacteria, and your symptoms are gone, so you stop. Then you have leftover bacteria that your immune system may or may not be able to handle, but you can still pass it to someone else who doesn't have an immune system primed to fight it off, so their infection starts with the 85th percentile bacteria.
That just makes my question stronger! So why continue the antibiotic till you create bacteria at the 98th percentile?
Stop the antibiotic as early as possible.
It's not like you're going to wait to infect people till you're done with the antibiotic, so the "starts with the 85th percentile" scenario still happens. But by taking even more antibiotic all you do (as far as I can tell) is make even more resistant bacteria.
I'm reaching the end of my knowledge, but I would guess that there's a good tradeoff between reducing the number down to 2% vs culling down to the "best" remainder. You also give your immune system more time to catch up and take car of the rest for you. If you can, with antibiotics, kill off 98% and prevent growth over a week, you immune system can probably handle the rest and you transfer 0 to the next person.
Because now you have ten times as many resistant bacteria going out into the world. They are marginally less resistant but they are still resistant, and you have so many more of them.
(all numbers arbitrary)