Sudden no engorgement

Once your breasts have regulated you won't have the engorged feeling anymore and it's a good thing! Less likely to get mastitis. You can check baby's weight over a few weeks, as long as it goes up constantly there's no worry. It's very unlikely that you don't have enough for your baby, your baby will keep demanding for milk if still hungry. Don't worry and take care!

Your breast supply is most likely regulating to your baby’s needs! You can pump after latching to try and increase supply / store for future growth spurts. But I would stress too much about it. At 3mo, it could also be that baby has grown to be very efficient at drinking and at ‘draining the boob’. So latching shorter time doesn’t mean drinking less

Yes, diaper output would be a good indicator if baby is feeding well. Power pump is a good way to increase supply, pumping 10-15mins after latching would help too. But i wouldnt worry too much if baby is latching well, and your milk supply would've regulated by now.

Take food that can increase your supply and do power pump!