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).
Don't forget, the self-employment tax is in addition to income tax. So plan to set aside 30 percent of your income minus expenses into a short-term savings account, and set aside money each time you are paid. Allocate for health insurance.