Extruder keeps jamming because of filament dust!
I'm highly unconvinced that dust in the gearing is related to your problem. If the material is still being extruded, then "in the air" suggests the base layers may have slipped, or your belts are slipping, either of which will lead to a huge lateral offset, and thus the "printing in air" problem. It's possible but less likely that the extruder feed gear itself is slipping.

If you can post a picture of one of these situations, that would help a  lot.  

I will mention in passing that there are several models for filament guides at thingiverse.com . Putting one of these on your machine will eliminate scraping and the resultant dust.