Spoke to an admissions rep. last year - she disclosed that they don’t care at all about the writing portion. FWIW. You are a desirable demographic with an ACT score above the 75th percentile so my guess is that you won’t need to worry about the writing. Completing the optional essays on the application can easily substitute if you have any concerns.
Colleges will unweight your GPA to assess academic prepardness. What is your uw GPA? If you don’t know it offhand just compute using A=4.0, A- 3.67, B+ 3.33, B = 3.0, etc. Weight each class equally unless you have reason to do otherwise (say, for instance, you have an elective that you trade off with another where both are weighted 50% on your transcript). Divide by the # of total credits. If it’s 3.5 or higher you won’t have much to worry about 3.0 - 3.5 you are probably still pretty safe given the attributes above. Less than 3.0 they might begin to worry about your level of preparation; however, guessing you aren’t in this category.
Earlier is better because they notify beginning in October (or at least that’s been the case the past three years).
Good luck to you!