Yes, "weird" is a possible translation, but probably not among 85-year olds. I checked my Hans Wehr (the English-language version), the Oxford English-Arabic dictionary, and the Mawrid English-Arabic dictionay, and all three list "strange" rather than "weird" as their most basic translation for "gharib"; "weird" may be with it in your age-range, but for translations with some merit, "strange" is probably still be the best even if not hip. The same argument goes for "a neighbor and a neighbor"--this is not a good translation, neither stylistically (so I am glad you came around to accepting my "two neighbors"; but it still is not a full translation because it misses out on the fact that one is male and one is female, while you pretend American unisex is good enough; and English is one of the few languages where there really is only unisex. I would think that "a neighboress and a neighbor" or "a female and a male neighbor" is taking care of the complete content, not just of a mutilated arrangement of words which is even stylistically obnoxious. "A neighbor and a neighbor"! Ha!
It can. Sometimes in casual conversation, the word "pretty" is used to mean "very." For example: The house is pretty big! But some people use it to show more of a middle area. For example: big, pretty big, very big. To avoid confusion, especially when translating, I would suggest using the word "very".
"Weird" means "very strange", in fact so strange that it couldn't be stranger. So you cannot say "Very weird". Just as you cannot say "very terrified" because "terrified" means so frightened you couldn't be more frightened. You could say "really weird" for emphasis. Using the word bank I would have had to say "very weird", so I typed in "very strange", but it was not accepted. I don't know why , since Duolingo accepts "strange" instead of "weird" in other questions.