First get yourself smart on the disability process and system. You can go to the DAV or such, but you should also look yourself on the VA website to go to the source documents.
For example, if you go here: VBA 38 CFR Book C (U.S. Department of Veterans Affairs)
and look up 4.71A, Schedule of Ratings, Musculoskeletal System, you'll find that you got to have a pretty gorped up spine to gain much disability from the VA.
If you're waiting on a medical board, you won't be allowed to reenlist, so that's not your issue. Do you want to stay in the Navy or not? You're halfway to retirement, do you want to throw away that pension and take a small VA disability?
Another thing to remember is that treatment on active duty is a far better deal than if you're out. You get paid, you get priority in treatment facilities, your command takes care of you. Go visit a VA hospital and see if this is better than your military treatment facility. We've got a great VA here, but it still does not compare to the MTF.
Finally, be aware that back problems are always suspect. Unless you have imaging that shows deformity (and even then most deformities don't yield disability or pain necessarily), or neurological deficits, or physical limitations caused by treatments (like spinal fusion etc) then it's going to be a tough road for you (whatever course you take) to prove it's a disability. Pain only don't cut it.
Free advice being worth what you pay for it, one final word from a former (multiple time CO): don't give the USN any reason to separate you. Don't neglect PFT tests unless you have a medical waiver, don't exceed body fat measurements, continue to perform well. You're a lot more believable as a good sailor who might have some physical issues, than as a no-load who might be trying to scam out on a non-existent medical issue. This is harsh, but this is reality.