Social Security is a non-issue. It works like this: if you were married for at least ten years, you have a choice when you reach full social security age - you can claim the full benefit based on your own earnings, or the spousal benefit which is 50% of his social security benefit (note: you can’t remarry until after you’re 60). If he dies, you can claim the widows benefit, which is 100% of his benefit (assuming this would be greater than yours). None of this affects his benefit or that of any future wife he might have, so it’s nothing to negotiate - it doesn’t affect him.
The only possible complicating factor might be if either of you has a government pension that didn’t pay into social security at all. Then there are issues with “double dipping” rules, which can reduce the amount of social security you get if you have a government pension that didn’t contribute to SS.
Attorneys are not all that great at the financial stuff, so good to consult with your accountant.
