One in 4 people has mental illness. So, pretty much ALL of us has someone in our family who has mental illness, it's only in the last few years that mental illness is finally losing it's stigma as a parental failure, so it will be less hidden, and people will begin treating it more. (previously viewed as a "nurture vs nature thing" and that's why family's hushed it up, society blamed parents)
Your kids will be fine -- fair, firm, consistent, loving. That's what they get from *you* and that will counteract the toxicity of *him*. If they do have mental illness, you're not going to lump a big bunch of guilt on your plate, because that does nothing to help, and none of this is your fault. You will watch, treat, and love, and they will grow, and thrive.
You totally got this, Mom. I'm not a hugger, but I'm sending you my version of awkward, arms kind of touching you, hugs.