Get an appointment with Soc Sec office. The applying person needs to answer questions and likely show documentation that they were married, and either still married at time of spouse's death or if divorced married 10 years or longer.

NO limit. Dr Ed says you can earn $1 Billion per month. 70 is past everyone's full retirement age

Medicare: At 65 you are eligible, but not required to start if you have insurance from your work or spouse's work, 20 or more employees in company. There is IRMAA consideration if you start it and your 2024 income was over $106K single or $212K married. This is a 2 year look back. The amount will change each year. It is not just one level, that is the first level. When you do stop working, you will need to get medicare if you do not get insurance from spouse. 2027 will have similar but likely higher thresholds. Soc Sec Retirement: Under FRA (67 for you) the limit is $24,480/year. Every 2 dollars over that limit you will loose 1 dollar. Without doing any calculating, I suspect you would loose all your soc sec income while earning this large amount. If you start Soc Sec benefit the month you stop working, this issue goes way. That limit also changes each year. There is a higher limit the year you turn 67, something like $65K Your actual question: At FRA, there is a recalculation that credits you for months you did not get Soc Sec. I think the acronym is ARF Adjustment to the Reduction Factor.

@Tarrelton Peffer Net income from self employment is what I hear Dr Ed say for the self employed. Gross income could be higher because of investment income

Leaving your job is a life changing event and I heard Dr Ed say you can file for this exception. I do not know if it will retro-actively apply to the past 18 months.