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).
The deduction is included on Form 1040, line 29. It may be helpful to look at Publication 535 for more information on the self employed health insurance deduction. Tax Deductions for the Self Employed.