I see someone already answered the how often on peroxide question. At work we use peroxide alot and recommend it to our clients. We've never had a problem with it. With certain severe injuries we do use the Betadine though instead. I suppose the peroxide debate just depends on the particular vet, what he/she was taught and what's worked for them for years. I'd say neither is really wrong or right, just different.

Anyways, Clavamox liquid is a particularly bitter tasting med (not that I've actually tasted it, just what the vets at work say about it). You might ask if they can flavor it if they haven't already, it might help a bit. Clavamox can also sometimes cause stomach upset, particularly on an empty stomach. Make sure your kitty gets a little bit of food either right before or right after giving the meds.

As far as squirmy, I can relate. I've had to medicate some seriously squirmy, and sometimes outright mean, critters at work. In those cases the wrapping in a towel like a burrito usually works best. In addition, I don't try to pry open the mouth on those types. I use my left hand (I'm right handed BTW), to hold the head still, my right elbow pinning the burrito kitty to my chest on a table or counter, then use my right hand to nudge the eyedropper into the side of the mouth. That causes the mouth to open and I squirt away being sure to keep that head still, and tilted slightly up so they aren't as likely to spit it back out. Then rub the throat a second or two to encourage swallowing, then quickly turn the poor critter loose. Later when they are calmer I go back and try to make friends again with it.

Here's a video of giving a cat liquid meds if that helps you any.

http://partnersah.vet.cornell.edu/node/305

Good luck.