Don't just sue for yourself. Sue to have all their employees reclassified as wage employees rather than salaried exempt, and try to get them to pay out overtime for all that after-hours work.
It would take an examination of the criteria determining the exempt classification.
FLSA 13(a)(17) covers "computer professionals".
If you do not use highly-specialized knowledge, or are not allowed to use your own judgment and discretion, you could potentially challenge the exemption. I would consider the number of hours worked in excess of 40 per week to be part of that discretion. And in my opinion, "at will" employees have significantly reduced discretion, as they can be fired at any time for any reason, or no reason, but I am not a lawyer, and I don't think any judge would ever determine exemptness based solely on that. It might be a contributing factor. If you're at will, and feel like working fewer than 70 hours/week would get you fired, a judge might strip off the exemption just from the pure horror.
But definitely read that section of the law, and ask yourself again whether software professionals need a union. That was specifically written for us--or against us, depending on your opinion of it.
Sue them like its going out of style.