According to the Commonwealth War Graves Commission, there were eight soldiers named William McBride, and a further six listed as W. McBride, who died in France or Belgium during the First World War but none matches the soldier in the song.
If you do not claim 100% of your self-employed health insurance deduction, you can include the remaining premiums with your other medical expenses as an itemized deduction on Form 1040, Schedule A (PDF).
If you're self-employed, you'll pay the full 12.4% but may deduct half of it on your tax return as a business expense. You'll owe another 2.9% in Medicare taxes on all of your earned income. Again, if you're employed, you'll pay half (1.45%) while your employer will pay the other half.