Anyone can sue for any reason, so technically yes they can sue. The only thing that they might run up against is a statute of limitations, but that would be state dependent and you did not specify the state. Additionally, I would think that 2 years is within most statute of limitations.
I am no lawyer, and as such this is not legal advice. This is what I ...
I understand that I'm supposed to remove all earnings attributable to this ineligible contribution--is there a formula for computing this?
That's if you withdraw (aka remove or correct) the excess contributions (by Oct. 15). See pub 590a 'Excess Contributions Withdrawn' for Roth and the more detailed version for trad which links to the same worksheet ...
You do not need to withdraw, you can recharacterize your contribution as a Traditional IRA then roll it over to a Roth.
Contact the brokerage.
Neardupe Where to enter earnings income when correcting excess Roth IRA contributions? (which I just updated).
How much to withdraw? .... Is this right?
It looks right to me, but when you request this Vanguard should (re)compute it for you, using the figures for the date the correction is executed. (AFAIK all IRA custodians do this, but you asked ...