Stay safe over there.
1. The experience will help you, but all you really need to do is qualify on the the ASVAB and be patient enough to wait for A school. There are other avenues to Maritime LE if it's your thing.
2. You will have to retake the ASVAB.
3. Here's the most current tattoo policy for the CG: http://www.uscg.mil/directives/ci/1...000_1B.pdf
4. You'll come in an E-3, the ME rating is at 100% and the A school list is a 4 year wait.
If you have any other questions, ask away.