Huge fan of the original Planescape. So much so that it overcame the distrust I had for WotC after all the OGL stuff. I picked it up and I have to say it reads as shallow. A lot of the names and content from AD&D version but written without giving any feeling to the setting created. I don’t recommend it.
I had the same issue w being unable to eliminate them entirely for ages. Putting a layer of sand over soil in pot was what finally completely resolved it for me (in addition to continuing all the other stuff you mentioned).