Are you using PETG? I've found all PETG suffers stringing, some brands worse than others, but it's always there and you'll probably always need to do some cleanup after a print. I'd use PLA for that job unless you really need PETG.
Also dial back your retraction, 10mm is a lot. Goal of retraction is to relax the "spring" of the filament in the bowden tube and relieve the pressure in the nozzle, not to drag the filament completely out of the heat block. You're pulling air back into the nozzle that has to get pushed back out again, and you're pulling molten plastic into the cold side of the heat break which could mean clogging.
I'd use support from the build plate, or better yet modify the design to put a ring or something to give it more contact area with the bed. Also dial back your acceleration/jerk settings, a thin part like that might flex a bit from being moved back and forth on the Y axis, creating print artifacts.
And definitely use Z hop. You don't need much, 0.2mm or even 0.1mm is OK.