Well the 50% deduction of the SE tax only goes against your regular income tax which we probably aren't considering. It does not reduce the actual SE tax on Schedule 2 line 4 which goes to 1040 line 15. I would use the regular full SE tax amount on that 1099Misc. Unless they (or you) just want them to pay a part of it.
Here is how it breaks out. You are paying 15.3% for both the employer (you) and employee (also you)
SS for employer 6.2%
SS for employee 6.2%
Medicare for employer 1.45%
Medicare for employee 1.45%
