unless the health insurance is for employees it does not go on schedule C. your health insurance should end up on schedule 1 line 17 if any portion is deductible otherwise schedule A. there should be a question as you go thru that schedule about your own health insurance. the reason is that SE health insurance does not reduce your self-employment taxes and is limited to net SE income. if you have improperly taken the deduction on schedule C in prior years' you have understated your tax liability and should amend.
as for other expenses, any logical method for allocating them is fine. That would include the home office deduction.
