Just make sure they don’t get swollen or inflamed. They’re made to supply what the baby demands so should be producing the right amount and if they’re soft at the end you should be fine.

You could pump after a breastfeeding session and see if there is more coming, you could also massage your breasts whilst feeding.
https://kellymom.com/bf/got-milk/basics/foremilk-hindmilk/

That’s a good question. I’m not sure how you would know if your breasts are completely drained! You can tell when they’re empty. I breastfed my babies and my son had colic, my daughter didn’t, as far as I know I did nothing different. Maybe your GP is sharing an old wives tale. I would be researching it more

well bub will be full lol. don’t stress. i just demand fed and they were fine. i always thought that the first milk was just watery and the other stuff was the good stuff