Before we say "possible failed" class, you need to know a few things.
First, have you looked over the syllabus' grading section to know exactly the grading policy? If you are on an absolute grading scale (x% = A, y% =B, etc), with a clear distribution of points (100 for quizzes, 100 for midterm, 100 for final), you can know where you are at with regards to "possible". However, if your course is graded on a curve, those absolute grades (60/100 on quizzes, 50/100 on midterm, ??/100 on final so far) tell us very little abou the "possiblity" that you are actually failing. You would need to know how your peers are scoring as well and the grading distribution (20% A, 40% B, 30% C, 10% D-F, or something to that effect). Beyond this, some schools/departments require a certain minimum percentage of passing grades, so even if there is an absolute grading policy (first item mentioned), the professor may be reuqired to figure out a way to get enough people to passing grades to satisfy requirements. In this event, you still need to know where you are in relationship to your peers. You mention this is a "sucky" prof. Is that for the entire class (nobody is getting it and lots of people are "failing") or is it just you not connecting with this guy? The answer is likely to have to do with how you are doing in comparison with your peers.
Second, you need to know your schools retake/replace policy with regards to "failed" grades and how your detachment deals with your GPA and your academic progress from term to term. Let's look at a couple different scenarios:
Scenario 1: You get the F and only get 12 quarter units out of 15 taken. Your school allows retakes to replace the grade in the calculation your cumulative GPA; - Given your 4.0 in the first term (15 quarter units), 3 A's, 1 B, and 1 F will yield a 3.0 for the term and drop your cumulative gpa to 3.5. Probably not the end of the world for you at the end of the second term, except that you are now behind on credits towards graduation. If your detachment has no problem with your retaking the credit in the spring (or even summer) to get back on track and your school allows grade replacement, you should come out of this unscathed (except for the extra work of taking the course again).
Scenario 2 - Your detachment has a real problem with your getting behind on units even with the retake/replace option in Scenario 1. Here, you must do everything possible to get that "D" or suffer whatever consequences there may be. Let's say you get that 3 A's 1 B and now 1 D and have a 3.2 for the term and now a 3.6 cumulative. Probably not the end of the world. If you have the retake/replace policy in effect, you get the same results as scenario 1. If you cannot retake, you will have some permanent damaget to the GPA, leaving you little room for poor grades going forward.
Scenario 3 - You get that grade up to a C. Now your term GPA is 3.4 and cumulative is 3.8. Not so bad, but now that C is probably forever on your GPA (no retake/replace available). Depending upon your school's retake/replace policies, your detachment's views on D and F grades, term GPA, cumulative GPA, and retake/replace, and your desire to retake a course in the spring or summer, you may consider attempting to get the highest grade that you can retake/replace option with. I don't always recommend getting a D+ in a course, but often if you can withstand the short term consequences to your term and cumulative GPA, it can be a better situation than the C- (being a non-retakable grade - check on this because some schools will allow retakes of C- grades) for your academic career.
My final point is not to freak out. My guess is that you've probably never had a grade lower than a B in your life. Your attitude towards your prof may be more a reflection on your processing the fact that you've never had a "bad" grade before. You need to check your attitude towards the prof (a skill you will need in the military because odds are you will get a boss who you don't see eye to eye with, given the number of times people rotate in the military) and focus in on what you can do to maximize your grading outcomes going forward.
Best of luck.