You're trying to cache the selector binding the jQuery validate. We send configuration variables with the binding. The spoof checking is sent with that as it's per page based. There is no changing this behavior and no plans to change this behavior. You really only need to be caching the files themselves.

Is there another way to validate ajax fields than these random strings ?

No, they're security strings.

Could you wrap the generate CB scripts so that we can exclude them ?

Wrap them? With what?

Could you provide a way to defer CB js at bottom so that website would be accelerated with main js cache file deferred too ?

No, JS reads top to bottom. This would entirely alter our entire JS usage and loading order and potentially break all of CB. The scripts belong in the header and no plans of changing this, sorry.

Sorry, but your issue seams more like a problem with JCH Optimize than CB. Sending generated values with a selector isn't abnormal by a long shot. JCH Optimize would need to be able to handle those cases or at least let you specify exclusions.

Yup, I highly recommend only caching static pages that don't change often otherwise you risk issues with data being out of date. In dynamic environments caching gets a bit complicated as some things can cache while others can't. I also recommend not caching forms or form endpoints as they often contain security strings sent with the POST.

Browsers do pretty good caching CSS and JS files themselves. There are optimizers that can merge them into a single file, but from my experience they don't work well and often break the JS.

Eventually we'll have a new CBLib API for better dealing with cache internally and automatically. Currently this is done often by static variables to avoid duplicate calls, etc.. However with an API library that can properly use PHP caching or fallback static variable caching we can improve this further. That's for a later CB release though.