How do we know it's bugs? ML said nothing to indicate an infestation of any sort although PR offers some good advice. A decent pocket scope will come in handy. Don't worry about getting the MG off the roots. Give it a very gentle shake and let any loose stuff fall away. Otherwise, just surround it with new soil. Perhaps flush first to leach out some of the nutes in the MG. 3 gallons would work but 5 gallons would be better. If you have no need for 5 gallon pots consider bags? The MG and FF has plenty of food. No more nutes or molasses until week 4 of flower and then @ 1/8 strength. Less is more! Don't over engineer it.