For me, it depends on where the wound/injury is.
Head/face/around eyes - I use saline. You can purchase saline or look up the recipes online. I have also used Banixx on the face as well...just saying.
Wounds on the body...you can use any of those you have listed. Peroxide could be used with initial cleaning if that's what you have on hand. Warm soapy water can also be used, just rinse.
Syringes can be purchased online or at stores like
TSC. I sometimes pick up larger syringes at
TSC, but for small 1ml syringes, I ordered bulk online I think off
Ebay, but do a comparison pricing at
Amazon as well.
I think sometimes we all get a bit hung up with what products should be used. It's great to have things on hand and be prepared if possible. Consider your budget when getting items for your chicken kit. If I could only pick 1 thing in your list, then I would get the Chlorhexidine or Betadine. Either one will cover just about anything and of course saline can be made at home with boiled water with salt added. (Dakin's can be made at home too - so having that recipe is a good idea as well -it's not one I would use on the face/eyes).
Go for simple and basic.
Also - triple antibiotic ointment - generic store brand seems to work very well for treating most wounds. I've used it on most everything from ripped and torn skin, toes/feet, eyes/face, bumblefoot, etc....this is something to keep on hand as well.