Here's what you need to do dude.
Work your butt off senior year, get your GPA up as much as you can. Apply in the fall for the Third Mate gig at MSC because you can always back out of it. If you want, submit a SWO package as well senior year if you can get your GPA up to the 2.8. It is highly plausible to go from 2.7 to 2.8 your senior year, Shiphandling 2 is really the only class that could trip you up on that. Just make sure you STUDY for the test at the beginning of each class. People tend to get focused on the mission planning and forget to look over the COLREGS (lights and sounds!), the 10 million "rules of thumb" for ship driving, and some generic basic seamanship stuff. People overlook Sea Term but rock that out, it can actually boost your GPA significantly (it did mine every year). Get A's in everything in the spring, there isn't a single hard class that semester since you're studying for your license. Load up on those PONY's for ship, meteorology, and cargo/containerization.
Then go do a tour with MSC, its a good point on the application for when you apply for OCS. The Boston OR is pretty familiar with your experiences and will work with you. While your at sea, study for the ASTB so you can get and outstanding OAR score. Every time you get off that 08-1200 junior third mate watch, go to the O-6 deck lounge and study for an hour. Everyday. Thats what I did and when I ended up taking the ASTB I walked out with a 72 on the OAR. Find some nerdy engineer to help you out with the more complex math and physics stuff in there because that's where you'll make your money for grades.
When you come home see if you still want to be a SWO, and go take the ASTB. I will caution you to make sure you really know what you're getting into in the SWO community. After sailing on your license, the way the surface community does stuff will have you in your space on a cruiser bashing your head against a bulkhead asking yourself "why, just why." (thats from experience). However (comma) if you really hate it, its a pretty minimal commitment and I will vouch three years goes by pretty quick. If you don't know anyone that has gone SWO from Mass Maritime as a deckie, shoot me a PM and I'll get someone in touch with you.
Finally, just apply for SNA. Flying beats the shit out of SWO or deck officer. If you decide you want to fly for the Marines, come talk to me.