> 2. Avg social security is ~25k/yr (mostly untaxed)

Where are you getting that number?

One source I found said that the average SS benefit in January 2019 was $1461/month which works out to $17.5k/year. [0] This seems to agree with the SSA's snapshot from May. [1]

[0] https://money.usnews.com/money/retirement/social-security/ar...

[1] https://www.ssa.gov/policy/docs/quickfacts/stat_snapshot/