Umm... To be fair, I can see from their perspective. I mean, OP is not completely not at fault here. He had a previous experience with another casino about similar situation, hence he asked in advance about gambling from Portugal. But he is not being specific to the support team about why he asked about it.

I think, suppose he explained in details why he asked if he's allowed to play from Portugal, about his past case with other casino and ask the support to clarify the matter to their legal team or other division with knowledge about this, the support can give a better and accurate response. But, since OP didn't mention the situation that prompted his inquiry, although probably unintentional, he lead himself [and the casino] into this situation.

The terms given by housebet's rep is a term that is used by many casino: that it is under player's duty to know the regulation in their own country.

In a way, from the other perspective, OP did know about this, yet he still played, and [sorry for sounding harsh and outspoken, but I am simply stating an objective observation here] seemingly omitted the info from his inquiry to the support so that the email to be used as reference in the future, suppose the situation he faced with other platform reoccur.

But, I'm not here to distribute blame. Rather, to deescalate matters. So, OP, do you mind to wait a little while I try to reach God of Thunder to get a contact of the casino? I'll see if I can get you both to meet in the middle.