I like that they're mates with the old guy now.
Come on, Yusei's mom and Femme Fatale both have their shit together, being reasonably successful business owners.
Yuusei calls her mom (母さん) in the first chapter, when telling Sumire that she owes her. Which btw, shows him as being a manipulative little shit, the stuff in the current chapter didn't come out of nowhere.
And attractive female company paid to entertain you and put up with your drunken rants.
Sure, sure, most snack bars are clean, but the mizu-shobai spectrum goes a bit like this:
Regular bar with pretty waitresses < Snack bar < Hostess Club < Grope bars, Brothels, Soaplands and the like.
Both...
It's a snack bar (スナック), more casual and less prostitution-adjacent than a hostess club. Other than that nitpick you're spot on with the rest of your analysis.
Ramen Saburo is also a reference to Ramen Jiro, a very excessive (and tasty!) ramen shop with a fanatical following and a somewhat hermetic ordering ritual.