Sweetheart, take it from me, someone who has been there and also survived. (Coming up for 20 years ago)
NOTHING is worth killing yourself over. Your children need you. YOU need you.
Work is work, a cheating h is a cheating H, but you can and will get through all this shit and actually, you WILL be stronger on the other side of this.
You know suicide isn't the answer. You don't need me to tell you that. One day you will look back and be proud of how far you have come, how you grew from it and how you know you can face anything.
Take one issue at a time and see what you can do to resolve it. Work? Could you quit? Cite constructive dismissal? I know it's a fight, you may not have the strength to take it on now, but find out if there is a one limit? Or get signed off and look for something else.
Your h is a cunt. His colleague also. The right thing to do would be to kick them both out of your lives and focus on your Dc and your own life and happiness.
At the back of my mind, hearing how much "release" you feel at discovery of your h cheating, I wonder if subconsciously you knew something wasn't right, but weren't listening to your instincts and THIS will have impacted dramatically on your mh.
In all events, we are all glad you are still here, I hope your family are supportive (mine weren't, so proof you can recover alone if you need to)
If you think your mil would be supportive, please open up to her and sil. Bugger awkward, what he has done is beyond shit, not only betrayed his family, but gloating about it too :(
Keep talking to us and to therapists if you have one, please get referred for some talking therapy too,
This is not the end of you, it's the beginning of the better, stronger you.