Bendaroo
There are loads of muddled issues here.
Yes, it's considerate to call someone if you have travelled away. BUT calling or emailing someone will not stop them jumping into bed with OW/OM 2 minutes later- would it? Someone can make a "duty call"- then do whatever they like afterwards. If you agree to trust someone- and they agree to try as well- then you need to back off and let the process take its course.
So your "keeping tabs" scenario and wanting security doesn't really stack up in reaity.
I don't think your behaviour could be classed as either " reasonable" or " unreasonable".
I do think you come over as insecure, determined to hang onto this guy whatever- when maybe being more feisty, less clingy, more " don't really give a fuck about you" attitude might stop him in his tracks more- and make him worry about losing YOU.
You don't seem to value yourself or have any confidence.
How old are the children? If he is 50 and you have kids young enough to make pumpkins etc then is he a lot older than you- or you had kids late? Is this is combo of depression, mid life crisis, pressures of kids etc- and a predatory woman offering kindness and escape?
If i were you- and I'm not- there is no way I could come onto a forum and ask for advice about cloak and dagger tactics.
If I were you, my DH would be met with a stony face when he came in, and my asking WTF are you doing going away with OW after all we've worked through.
If he asked how I knew I'd tell him to mind his own bloody business how I knew- I just did. he would then be worried whether it was friends whod told you or whatever. You don't NEED tell him how you know!
Then I would have a bloody good talk with the kids out of the house or in bed about what was happening and what he and you want from your marriage.
I think you need to " grow a pair" and just face the situation head on.