How do i possibly keep a single tooth 5mm gum pocket depth clean from food and bacteria build up until next cleaning? hygienist said after: when it gets deeper or other problems the tooth will be pulled. (??

See a periodontist for possible gingival recontouring to eradicate the pocket. You will have a tough time keeping a 5mm pocket clean

You have a problem that your General Dentist and his Hygienist, no matter how talented, find to be slightly outside their comfort zone. please seek evaluation bye an oral soft-tissue specialist, a Periodontist, who may have multiple additional options available.