Cheater ?

Probably not

Sure, why not? If you think sending dick picks is a reasonable reaction to a comment like that then I can't see why you'd have a problem with an unsolicited one.

Umm..? What's not to believe?
1. This is an admission to a firable offense. That's clearly sexual harrassment against her coworker. Even if she made said big trucks "joke"
2. Even if she made said big trucks joke and explicitly requested the dick pic? That doesn't absolve his actions in terms of you and his relationship.

HE seems like a scuzzbucket. Why haven't you dumped him already?

You need to bin this guy asap. I say that as a man! What else does he get up to, that you arent aware of?

How do you know this, anyway? Were you snooping on his phone or did he tell you? Why in either case?