Dear Stefan, thank you for your comment.
To sum up, your very interesting argument is that in absence of an absolute impossibility, everything is possibile, even that everything is not relative.
This is another version of the paradox of §6. Regarding the absolute relativist point of view, the process is similar as the one I described before: the truth of this new argument is relative to the parameters I adopt - not only logical parameter, even factual ones.
We can't conceive a world (physical, logical...) without the principle of contradiction or other basic logical rules that makes these truths possible - but ours is anyway relative to these rules.
To say that everything is not relative is like to live in a red world showing a red card to demonstrate that everything is not red, because the card is a square.
As you point out in the rest of your comment, without an absolute impossibility, every kind of absurdity is possible. This is not really a problem, because absurdities are possible only relatively to different rules, where our basic principles fails.
Regarding solipsism, it sounds more like the skeptic problem. How can we state for sure the truth of the external world and of our senses and intelligence? We can't, of course. But that there's not an external world could be a deception as well.