Items 1-3 are already adjusted in row E of the QBI Deduction Info worksheet at the bottom of Schedule C and the K1 worksheets (and other forms that generate QBI). I would need an example of what you're talking about regarding 4 & 5.

As far as using the Proposed Regs to avoid backing out SE deductions, the IRS has made very clear that's not permissible. The silence of the proposed regs with respect to SE deductions was not a statement that they should NOT reduce QBI. Even under the proposed regs you had to back out any deductions connected to qualified business income, the final regs merely specified that yes, the SE deductions fall under that category.