Hi, I haven't read all the posts (just yours), since I'm trying to Catch Up in a Hurry, so I don't know if anybody else has suggested this: OP, early on, you mentioned that his workmate collected him. Others suggested that this may well be a ruse, I saw one poster even mention an entire ring of cheaters "going out to work".
Your ex-DH's workmate is aiding and abetting cheating. Is he married? Do you know his wife?
You see where I'm going with this... I'd seriously consider giving her a ring and telling her what you know about your own exDH, it's entirely up to her if she chooses to employ the element of surprise in checking her own DH's texts, etc.
Honestly, this is the only contribution I can make because I think you're doing brilliantly! I accept that you might be feeling like a walking pile of jelly inside, but I'm blown away by how strong and resolved you are and - for want of better word, sorry - efficiently? you've turned this corner.
Thanks. I don't feel strong at all, I think I'm in autopilot. What's the alternative? Have him here, give him another chance, constantly worry everytime he goes out, check his phone. I couldn't live like that, it's mental tortue. This isn't a walk in the park but it sure as hell beats all that. I don't want to end up a paranoid wreck. I'd rather suffer this pain knowing it won't last forever.
^^ This - there should be a Mumsnet statue of you. You've got a clarity that is almost amazing at this stage in the process.
And what Fairenuff said about character - that too, with bells on.
It is said by wise people that courage isn't "never being afraid", but pressing on despite your fears. I think strength must be defined not as "never feeling weak", but doing what's right, no matter how weak you feel or how hard it may seem.
If your FW learns nothing else, he'll learn that he can't get away with things like this and women aren't that dumb. OK, that leaves several billion more men on the planet that need their own lessons, but it's a start - you've done your bit! 
Sorry, long - but sometimes a thread will stir me to sheer f&^%ing (probably bad) poetry, and you, non-Loserville are one of those times.