There are a few things I would add to the list, standing wraps and quilts. They work great for a horse that is on stall rest and is prone to getting stocked up. I also use them for older horses when shipping long distances. Lots of good bright flashlights and battery powered lanterns. We would all like to do all doctoring in a nice well light clean barn but that is not always possible. Also, make sure you have different forms of the bute and banamine. I keep both the paste and powder form of bute. The injectable and paste form of banamine. I have a horse who does not take pastes well and one who does not eat the powder unless I drench it in molasseses. Oh, and that is another thing you should have molasses, works great for encouraging a horse to eat meds. I also, keep a couple different antibiotics on hand, Penicillin, gentamicin, and SMZ's. Also, keep a locked fridge in the tack room. A small dorm style one works fine, penicillin must be refrigerated and it is nice to be able to put the drugs right into a barn fridge if something that your vet prescribes need refrigeration. Lockable because somethings are narcotics and people will steal them. I also keep the banamine and bute in a locked container. Also, if you are at a boarding barn, you don't just want anyone to start injecting horse even if they think they are doing the right thing.
And yes my vets number is on speed dial, likewise is my friend who works as a tech for him. I encourage you to find a good vet who you are comfortable talking to and will answer all your questions. I have a number of other vets on my phone too in case my vet is out of town. I have them listed in order of who I like the most. Unfortunately, the night my mare got hurt I had to call vet number 3, as my vet was up at a horse show hours away, but I sure was glad that I had his number. Vet number three is cheaper then my vet but not worth the money that you save.
About the whole hydrogen peroxide thing. I do not use it on wounds anymore, but I do keep a big bottle around to help clean areas around the wound. For example my mare has a wound 'above her hind leg' (to put it delicately) and now she is draining from the wound on to her whole leg. I use the peroxide and the foaming action to clean the drainage gunk off her leg. I already have to spend too much time back there for her taste and I don't want to spend tons of time scrubbing, so the peroxide helps me clean her quickly.
Also know your horse's normals, in other words what is their temp range normally and how quickly does their skin go back when they are hydrated. This way you know what is different for your horse.