If that were my duck I would probably make sure I had an area where she could keep her feet dry after wrapping. I would start again with the big swelling on the middle toe, pull the scab, squeeze out whatever gunky stuff you can get, and pack with triple antibiotic ointment the first day, gauze pad and vet wrap. You don't need plastic, I've been through that and it isn't necessary. Just keep her out of the water so she keeps the foot dry. If you want to see pictures on how I wrap the foot I'm happy to send them. After 24 hours, re-bandage after you slather on the epsom salt poultice:
https://www.amazon.com/dp/B001OE3L8...amp=&crid=1Y9Y5CWUQWH5B&=&sprefix=epsom+sa. I would keep this up on and also use the poultice on the heel, but I wouldn't cut into that one right now - seems like the lighter brown scab might indicate healing. It just takes a long time. If after 4 or 5 days of keeping them wrapped with the poultice you feel like the swelling is going down, you could then stop wrapping and just scrub twice a day with colorless iodine and a toothbrush, keeping them out of the water for 30 minutes afterwards. These are just things that have worked for me and I've been dealing with similar ones to you currently on the middle toe. Just keep at it and make sure it's not getting worse. Antibiotics alone will not clear up the infection - it has to be drawn out of the foot - that's what the epsom salt poultice works on.