How do I remove mold seeping from under the toilet?
By scraping away the mold you are only treating the symptom, not addressing the cause.

The mold is being fed by leakage from the toilet or drain.  The odds are more than 99% it is coming from a leaking waste connection.

To fix it, remove the toilet, clean it up and reinstall.

The directions for removal and re-installing are here.  You'll need a $6 wax ring and a couple hours depending on the condition of the fastening bolts, how handy you are, and luck.