Hi Alice, after reading your background and questions listed here, I feel like you need to do more research of this field.
SLP is a very competitive field filled with talented, and hardworking individuals. I don't know if retaking those classes will help and I suggest you talk with your CDS professors to ask for their professional opinions. 3.15 is not absolutely hopeless because I have seen top 50 graduate programs take in students at that GPA range, but indeed rare. The current emphasis of needing bilingual SLPs refers to mostly spanish/english fluency, not necessarily Chinese/english fluency. So even with most schools who offer bilingual track, they want students who speak fluent spanish. Personally speaking, I don't feel like being an international student/permanent resident will make that much of a difference. I am a permanent resident now and applied as a PR instead of an international student. You can just elaborate on your international background in your personal statement. Why bother to ask for higher tuition?
To counter low GPA, I'd say the rest of the package better be killer good: GRE, rec letters, and personal statement.