What you are essentially arguing is that there are sufficient push-"backs" in the system to counter a slow, steady push-forward in a single direction. It's fine to think or hope that, but it's not scientifically defined as likely. The models can and do cover the systems that are involved. That does not deny there are uncertainties; the predictions come with associate uncertainties.
That's one of the most idiotic analogies I've ever heard. I say one of the most idiotic because it's typical of the feeble minded BS that comes from most global warmers.
It was not so much an analogy as an illustration. If you want an analogy; take a bathtub and fill it nearly to the brim with water. Turn on the faucet, and open the drain. Provide you have enough incoming water flow, balance the incoming flow with the drainage so that the water level is stable. Clearly there will be turbulent circulation in the tub, temperature variability, etc.
Now start adding a teaspoonful of water from the sink next to the tub once a minute. What will happen to the level of water in the tub?
The point of the analogy is to show that a small steady change in one direction will influence other variables in a system in one direction.
Your analogy is still flawed. Heat doesn't escape the earth through a fixed size drain, it is reradiated and reflected into space. Both of those are affected by weather which must be modeled to determine the resulting heat loss. A GCM without a weather model might be like your bathtub scenario. But the real earth is like a tub with waves that splash water over the sides. The real earth doesn't reradiate heat evenly using a single parameter like your bathtub drain. In the real earth the vortexes change how energy is lost into space, unlike your bathtub where they don't matter. Finally the extra water vapor in the real earth as postulated by the forcing theory, does affect the weather and therefore the energy lost to space.