你老竇個仔, is it a minced oath in this case? If so what would be the original meaning? I'm talking specifically about this scene. I'm trying to translate this to english but as of now I don't know where to start.
Yes, it is. Cantonese swearing can be very vicious and graphic sometimes.

The most common Cantonese swearing is 「我(F)你老母」and one of a variants is 「我 (F) 你老母個 臭化(C)」; 臭化 means smelly and rotten. 


  「你老竇個仔」 is a minced oath for 「你老母個 (C) 」, short for 「我(F)你老母個 (C)」


Replacing "老母" (mother) with "老竇" (father), and replacing the Cantonese "C" word with a similar sounding word "仔"

To translate it into English, you can use any minced oat, as long as it expresses strong disapproval. 

For example: "Gat Dangit" --> "God damn it"