I can´t be positive, but the way you talk I assume that you got it well. Yes.
I think the "should" in some cases, has that r-sound to it (or almost), as in the song "I should have known better
". Let´s wait for further comments, though.https://www.youtube.com/watch?v=OWGNnkReiag
Sometimes it´s difficult to explain in terms of Portuguese. It´s difficult to an ESL to explain, since it´s on the realm of phonetics.
A good place to starthttp://soundsofspeech.uiowa.edu/english/english.html
I mean, in the "I should known better" in fact may not have an r-sound as in Portuguese, it´s something on the process in the mouth that makes the sound seems like it. Sometimes the "d" takes an r-sound, though as in "should I stay or should I go."