He doens't tell YOU where he's going when he LEAVES does he?
As for his pathetic solution to his marital problems... Texting you he is likely doing secretly and not telling OW... so i am thinking keep that up.. NORMALLY I wouldn't reccomend ANY contact...
Given his behaviour today though.. I would make him sweat for at least a week.. not a single text back to him... let your friend screen all the texts and calls.. BETTER YET.. swap phones...
let HER answer the phone and she can tell him you arne't available to take a call right now