Here's some general info on heath ins and Schedule C.
Self-employed health insurance deduction goes on Form 1040 Schedule 1 line 16 which flows to 1040 line 8a as long as the expense is not greater than your Net Profit on Schedule C individually. If the insurance is more than your Net Profit on each of your Schedule Cs you can split it up and enter part on each Schedule C so you don't go over the Net Profit on either one.
If your health ins exceeds your net self-employment income it gets split. An amount equal to your net self-employment income goes on Form 1040 Schedule 1 line 17 (to 1040 line 10) and the remainder gets added in to medical expenses on Schedule A.
