"Still using the example that Sched C business is TP name only."

Doesn't matter, because it is not always possible. More than once, the IRS describes this does not matter, so set that aside. "The insurance plan must be established, or considered to be established..."

And before we continue to break this down further, I want to explain parity. The "name" issue falls here. There is a move to parity for the self-employed individual, as we saw during covid-19 with the FMLA/Sick Leave provisions. SEHI is a perfect example. An employee might be offered a menu of health insurance options by their employer, including self-only and family coverage. Have you ever shopped for health insurance for a business? The self-employed individual typically can't get a group policy without at least 2 individuals (outside of the number in their own family coverage). The 2012 interpretation moves closer to parity, in that the self-employed person can include their own and/or a spouse's separate coverage and even Medicare coverage, which is not a family plan nor in the name of the self-employed business or even the self-employed person, because there is no provision for Medicare to be anything other than in the name of the individually covered person. It provides parity, then, for that person's individual coverage, spouse and qualifying children to be includable in the SEHI anyway. Business owner on Medicare, spouse on ACA policy? Add it all up, as if it is a family plan under an employer = parity. What I like to see is the ACA account owner is the business owner individual, and the covered spouse is the insured. That's often as close as you can get under ACA for, "this is my business benefit tool."

You know about the 2012 reference, but here is an earlier one:

https://www.irs.gov/pub/irs-wd/0524001.pdf

"One of the reasons for enacting the ' 162(l) deduction was that the existing rules relating to the exclusion from gross income for benefits under employer accident or health plans created unfair distinctions between self-employed individuals and the owners of corporations."

"1) Would the SPOUSE post-tax 1099-R retirement plan health insurance"

There is no such thing as how you are thinking of it. You have the plan and you have the payment method. The 1099-R is simply about money moving to a person as a retirement benefit or from an account or annuity or other provision. You stated the spouse is covered under Medicare. You can be on Medicare (at 65) but not Social Security (delay until 70), so you need to pay those premiums separately. The same is true for dental or that supplemental plan. Avoid a double-dip; if the ex-employer pays for the supplemental, or the employee has a pre-tax deduction for that supplemental coverage, then it's already got a tax benefit.

https://www.irs.gov/instructions/i7206

“Medicare premiums you voluntarily pay to obtain insurance in your name that is similar to qualifying private health insurance can be used to figure the deduction. Amounts paid for health insurance coverage from retirement plan distributions that were nontaxable because you are a retired public safety officer can’t be used to figure the deduction.”

And even that statement recently has been updated for parity. You don’t include the cost as SEHI: “If you are a retired public safety officer, amounts excluded from gross income, not to exceed $3,000, if the amounts (1) were paid by your retirement plan directly to the insurer for qualified health insurance premiums or (2) received by you from that retirement plan and used to pay those premiums.”

If the spouse’s supplemental coverage premium is paid as post-tax deduction, then that would be the same as the retiree made the payment (but indirectly), the same as a Social Security recipient is doing routinely for Medicare.

"2) From 2012 Memo, Medicare premiums for TP/SP are ALL deductible as long as Sec 162(l) conditions are met"

Exactly.

"3) Sec 162(l) condition paraphrase = If TP is merely eligible for any Employer Subsidized coverage (through TP or SP)"

Your taxpayer’s spouse has supplemental coverage, but is that made available to the taxpayer? If no, move on. Is any portion of the premium paid by the employer? If no, then it is not a subsidized plan. That's why this really is a much simpler issue than you are making it.

"But retirement coverage is likely not subsidized, therefore OK to deduct Medicare."

Medicare is never subsidized by an employer. The Supplemental plan might be, but perhaps the taxpayer couldn’t be covered, even if he wanted it. What does “retirement coverage” mean here? It’s just coverage. Retirement is a status. Even CMS (Social Security Administration) deducts Medicare premiums post-tax. If the spouse's ex-employer pays for the supplemental plan (that is not one of the Medicare lettered plans), that means the taxpayer-spouse aren't even incurring it, so of course, you don't need to include it in SEHI.

"So at this point, I think I can only deduct both Medicare premiums. Likely can NOT deduct the Spouse Retiree premium since the 2012 Memo was only about Medicare & the 7206 clearly states the policy must be in the name of the business or the individual. Does that make sense?"

The "&" is clearly out of place here. I think you are only debating the Supplemental coverage.

The reason it's "only about Medicare" is because the ruling was needed to decide if non-private coverage (old age, public) applied. The "name" issue, of the business or individual, is already defined:

https://www.legalzoom.com/articles/what-is-the-self-employed-health-insurance-deduction

"The self-employed health insurance deduction allows some self-employed individuals to deduct the premiums they pay for:

• Medical insurance
• Dental and vision insurance
• Qualified long-term care insurance
• Medicare premiums

If you qualify, you can deduct the premiums you pay for yourself, your spouse, dependents, and children under age 27, even if they aren't dependents."

Just go with the facts.