I'm thinking I should tackle his worm problem first, & then his feather cyst.
OK The syringe you have, the lines are graduated in .20ml, I took your photo and added some numbers to it, as a visual - that may be easier to understand than my typing.Wormer won't be here until either the 28th, or 30th. Suggestions on what I should do until then? Even though he's pooping, he is struggling abit to do so, like he's abit constipated. Possibly due to the worms.

Do you have a Tractor Supply, Rural King or similar store that may have the Safeguard in store? If so, and you can get the dewormer sooner, that would be best. I understand if that's not possible.
Can you get some photos of all of him?
Does he have only the one place on him with the feather problem or are there a lot more?
Is his crop emptying?
Do you happen to have any antibiotics on hand, if so what?
Struggling to poop, you can give him 1 tsp coconut oil twice a day for a couple of days. The poop is concerning to me. I would be inclined to treat for Coccidiosis, give him an antibiotic like Amoxicillin and deworm him. Feed him some white cooked rice with buttermilk. Chick starter for his normal feed.