I will respectfully disagree with the use of Wazine or Ivermectin as dewormers. Wazine is only effective against round worms and there are many other internal parasites your chickens will pick up. The effectiveness of Ivermectin is on a downhill slope in chickens, my avian vet does not recommend it. You might consider Valbazen, it will take care of anything a chicken can pick up. If you use that in rotation with liquid Safeguard goat dewormer you should be in good shape.
As far as first aid to keep on hand for chickens... I don't keep all that much. I use plain saline to flush wounds and then apply regular Neosporin (NOT the kind with pain reliever). If it's a wound that's visible to the other chickens I'll apply BluKote. We very rarely have any such injuries to treat here.
I keep Corid on hand, especially with chicks or young birds in case of cocci. Seems like stores are always closed when you need it and that's something you don't have time to wait around to treat.
My chickens have never had lice or mites but I use Garden and Poultry Dust and treat the coop twice a year anyway.
Electrolytes, like Save-A-Chick are helpful to have on hand in case of slow, stressed chicks or heat stressed hens.
I do keep antibiotic's on hand, I have Tylan 50 as well as Amoxicillin but I only treat with antibiotic's when I know, or have a very good idea, what I'm treating.
That's about it at my house!