If they are gnats I wouldn't be too worried. Here's a few simple tricks to keeping their numbers stunted and/or eliminate them.

Water the soil with hydrogen peroxide. Not a lot, maybe a capful per gallon. Only do this when they seem to be getting out of control

Get some yellow sticky traps and position them around your pot. This should catch the majority of them

Cover the top 2-3 inches of your pot in perlite. They will have a very hard time surviving with a dry surface. This also means that the drier the soil, the better chance you have at ridding them.

If you want to rid them completely do all 3 of these at the same time. If this still doesn't seem to work (unlikely), next step would be a product like Gnatrol or Mosquito dunks

As far as everything else, the advice you have gotten is spot on. Except for chucking your plant. The soil should have great drainage with the added perlite. Now that the roots are breathing, growth should explode. You didn't mention what you used for the new transplant. What soil? Did you add perlite?

No pest strips are great but they won't work unless the room/box is sealed for a period of time. Whenever I pick up new clones I let them marinate in a small box with a no pest strip for 12 hours. It will kill everything if there is no ventilation (mites included)

Foliar feeding should be done at 1/8th strength or less

Well, thats everything I can think of, I hope your plant gives you some massive buds