To "rebut" your points, then:
1. True, but one could be forgiven for thinking that the "just" in "amount of CO2 in the atmosphere is just 0.04% of the total" is extremely loaded. Nobody disputes this figure, and the fact that the concentration of CO2 is small compared to, say, oxygen, is neither here nor there in terms of the discussion.
2. This is another case of being extremely misleading. Roughly speaking, human activity accounts for about 30-40 gigatonnes of CO2 (GTC) annually, compared to around 750 (GTC) annually from natural sources. However, this is to ignore the fact that while natural sources dump 750 GTC into the atmosphere, they also suck it all back in again, eg because plants use CO2 in photsynthesis. Natural processes are in various variations, so it isn't true that the sum is exactly zero annually; instead, in some years natural activity would increase CO2 levels, and in other years it would decrease. There are also seasonal variations in CO2 levels. But in any case, the *net* natural changes to CO2 levels are measured in a handful of GTC.
There are few aspects of human activity, if any, that act as natural CO2 sinks. Therefore, the 30-odd GTC we dump into the atmosphere annually cannot be entirely absorbed again by the natural carbon cycle. The result is that, while human activity is directly responsible for around 3% of gross CO2 emissions, it leaps up to a much higher percentage of the net change in CO2 levels per year. Owing to natural variations, there is no sense in giving an exact percentage, but the most generous assumptions would show that human activity is responsible for around as much again as the largest natural change in any given year. Human CO2 emissions are, by the way, still increasing. Even in the last decade, we went from around 38 GTC to 43 GTC.
See, for example,
https://www.ipcc.ch/report/ar4/wg1/ ; also
https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/95JD03410 which compares natural and human changes in CO2 levels for the past thousand years.
3. True, not worth rebutting, except to state that since Climate Change is a global problem then obviously it will require a global solution. I don't believe that there's anybody labouring under the delusion that the UK alone can solve the problem.
4. Another extremely misleading bullet point. There are two basic replies. The first is that, even while water vapour does account for the majority of the warming effect (around 60%), that doesn't negate the importance of the other 40% or so. The second is that water vapour levels are in practice an effect, not a cause, of temperature. See
https://tinyurl.com/3kda66tu
5. Already rebutted to the extent that the second half of your point is mathematically meaningless. But the other point is that this ignores that the rate at which CO2 emissions are increasing is growing itself. Thus, even while doubling CO2 levels has less and less of an impact overall, we're taking a more or less constant time to double anyway. See also
https://skepticalscience.com/why-global-warming-can-accelerate.html
6. Another fact taken somewhat out of context. The rate of change is also relevant, and there is also no claim being made that CO2 concentrations are the only factor in determining the climate. 500 million years ago the distribution of landmass was also very different, and, for that matter, most animal life was ocean-bound, so that higher atmospheric temperatures were less relevant in affecting life.
Continued...