Your W has behaved badly for some time. For the past few weeks her "reward" for behaving badly was you taking her out on dates.
Your W behaved badly before Retro and her reward was you still attending Retro.
Your W behaved badly AT Retro and her reward was leaving (what she wanted) the being rewarded with a settlement (what she wanted).
She pushes you to your absolute limit in a very manipulative way, you cave and she plays on your compassion.
See an attny TOMORROW and get everything you discussed in writing and give her a VERY limited time to sign it.
WAS have a tendency to offer leniency and a cooperative spirit when negotiating "no the fly" (as you both did - negotiations were fueled by many drama filled days) tend to backtrack once they realize what they agreed to.
I would begin tomorrow making plans (closing accounts, getting things in writing, making this legally binding) and so on. Stay dark and NO MORE TALKING to her aside from your son. If she sticks to this Agreement then you have no reason to further discuss finances and paperwork can be exchanged via the mail.
Your W is high drama. The high drama WAS doesn't stop being high drama but you don't have to indulge her any longer. When her words no longer could control you she went to extreme measures to get her way (pills, gun). You let that "slide" once, don't make that mistake again. While this is a degree of mind reading it worked for her once and when she feels like she is backed in a corner again (financially for example) she will take extreme measures again.
Remain loving to yourself and your son but remove her totally. You can't even begin to heal with her so present.