There are no laws barring the sale and purchase of absinthe in Poland. Whether a particular store stocks it and whether suppliers import it is thus a matter of supply and demand. If you are interested in a particular brand, you may be able to order it from a retailer, provided they can find a supplier that serves the Polish market.
I'm sure I've seen absinth (not the brand you mentioned though) in the supermarket in Galeria Krakowska 2 weeks ago. Also I have seen Xenta Absenta in one of the 24/7 Acohole shops in the Kazimerz district of Krakow. Specifically the shop on the Miodowa street, 21 or 23, don't remember the number of building precisely.
I have seen Absinthe in many places in Poland inclusive of Carrefour, there is a specialist company ' Wine and spirits ' they have absinthe in stock. On the parter level of Zloty terrace in Warsaw there is one store opposite Hugo Boss which sell 3 or 4 different kinds of Absinthe.
Absinthe is not anymore what it got famous for: alcohol with wormwood which has halucinogenic qualities. Now this is not produced and todays "absinthe" is not something that would allow you to see the green fairy. You might just as well buy vodka or brandy, works the same.
Probably not. More likely due to suggestion. No good evidence has ever been found that wormwood is halucinogenic or has any significant psychopharmalogical effects at the doses found in absinthe, even in the old days. It's basically an urban legend.
Try Slivovitz especially the 70% version, it is normally drunk for Jewish passover. It will certainly warm parts of your body other drinks will not reach. DO DRINK IN MODERATION.
While I agree Absinthe does not cause you to see "green fairies" or any fairies for that matter the buzz is different from regular spirits. A vodka or rum buzz is very busy and loud while the Absinthe experience is much more sharp and focused. It's almost like you're not drunk but you are. Kind of hard to explain if you never experienced it. No wonder all the writers and philosophers of the 19th and early 20th centuries drank it.