Oh I understand what you're going through.
I found evidence of my ex's affairs. And I kept digging and digging for more evidence. Until I thought, no more! I don't need more evidence in fact I don't need any evidence.
I know he's a lying gaslighting prick. I don't need to show proof to him or to his parents or to anyone! I know and that's enough.
You don't need anymore evidence, you don't need to see the messages or proof that he shagged her (he did).
What he's done, telling you to kill yourself, having a burner phone, is more than enough to end a relationship.
You sound like the scales have fallen from your eyes and you can see him for the dick he is. Good. Remember that feeling.
When he realises you're serious and he's about to lose everything, his whole attitude will change. Crying, begging and probably threatening to commit suicide himself.
His behaviour will probably range from being angry and abusive, sending awful texts, to crying and weeping.
But whatever lie he tells you, post on here.
I wish I'd done the same thing on mumnset. Instead I wrote it all down on my phone. Every single lie he told me. At one point it was several a day.
Then next he said I was a psycho bitch, it was all in my head, I could look at my notes and the dates and be reassured I wasn't going mad!
I feel for you OP, your emotions are going to be rollercoaster for the next couple of years. Be strong. You deserve better.