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 paid non-reimbursed premiums for health insurance for yourself, spouse or dependents, you can add 100% of that amount to your other qualifying medical expenses as a tax deduction. You cannot, however, deduct any of what you pay for employer-provided health coverage, as that is taken out of your pay pre-tax.