Thanks for the detailed answer!
I came to the same conclusion as you about "Other Contributions Previously Taxed by MA", and I assume I got the IRAs I "own or contributed to" question correct since the TT-generated form 8606 appears to correctly account for the conversion and computes the taxable amount to only be the pre-conversion earnings/gains from the t-IRA.
I still don't know whether Roth conversions should count towards "Total Distributions Received in Previous Years" and I left it blank as well, but may revisit researching it for 2019 taxes.
