1. if your figures are right about costs/revenue then you are right the tax is too high to be justified on grounds of “internalising the externality.”

2. aside from intervening in markets for efficiency reasons governments need to raise revenue, the way in which to do this which incurs the least distortion is to tax goods with inelastic demand (cf. Ramsey rule), unfortunately, as you point out, things which have inelastic demand are typically disproportionately consumed by the poor.

3. There is a (somewhat) reasonable argument for separating issues of equity from issues of efficiency (cf. first and second welfare theorems) which goes like this: raise tax in the least distortionary way and if you dont like the resulting distribution of income then redistribute using income (not prices), the problem with this is that income transfers are also distortionary.

4. There is some literature now that people have serious self-control problems in the short run, using this line of argument you could justify the increase by saying: people would really like to quit but cant in the short run, increasing the price helps them to quit. i agree that this is paternalistic, but what you could do is ask smokers how they would feel about an increase in the future (not now, obviously).

Hope this is helpful.