Vinegar counteracts drano. If any question some could still be on dishes, give them a vinegar soaking. Also, if you get drano on your skin, quickly put vinegar on it to keep from getting a bad burn.

It would've been much easier to put a bucket under the sink and remove the trap.

Rinse them 100 times. Then after that, rinse them again. That stuff is highly toxic. If your sewer pipes are on a septic tank system, you just killed off most of the good bacteria. (add RidX) If you are on city sewer system, don't worry about it.

Not without a MAJOR washing. Scrub the sink basin & then scrub everything that was in it...