Take the following with a grain of salt as this year is my first time applying to PA school and I have not yet been accepted. I have however worked as a paramedic for the past ten years.
1. I completely agree with rev ronin in that paramedic school would not help but working as a paramedic would. My understanding is that since PA school accepts such variable PCE and HCE that they treat everyone the same. A PA student that received PCE as a paramedic is taught the same as someone with CNA, RN, Corpsman, or scribe experience. Would work as a paramedic and paramedic school give you an advantage with certain subjects? Sure. But in other subjects other people would have the benefit of different past experience/education.
2. Paramedic school and working as a paramedic does not guarantee you an interview. When I completed my CASPA I had around 28,000 hours of PCE working as a paramedic and I was denied an interview from one of my schools (and this was the school that specifically designated work as a paramedic as having a large and positive impact on receiving an interview). If you plan on working as a paramedic for a few years and then applying, I imagine it would help your overall application. However if you plan on simply getting the license without working as a medic, I don't think it would be all that helpful.
3. Paramedic school may or may not count towards your CASPA GPA. I took my paramedic and EMT program through a community college and as such received college credit for those classes. CASPA counted those grades towards my sGPA and cGPA. A co-worker that applied this cycle as well received his training through a private EMS agency's education department and so had no college transcript and therefore it was not factored into his CASPA. This is something to take into consideration.
4. A paramedic license does not guarantee you an interview or admission but not having a Bachelor's degree will definitely be an impediment to getting in. To my knowledge, no school considers PCE to expire so you can be out of the Navy for a few years and the gap shouldn't count against your application. Will taking the time off from school to get the paramedic training cause any of your prerequisites to expire?
Obviously, no one can make this decision for you except you. But if it were me, I would focus on finishing my undergrad. You can also contact the PA schools that you are interested in and ask them "Do you value training/experience as a paramedic to be higher than other experiences?"
Best of luck and I hope this helped.