Have i got this riight?- So their reason for being in contact for business finished a few months ago, they are still in touch, they have nicknames for each other and now they have dinner together at "your" restaurant which was special enough to you for your dh to take you to for your anniversary. This is not a business dinner, as the business reason stopped.
You found out because she posted on her fb- are you a friend of hers on fb?
Its unusual a business person used to going to smart places would post a pic on fb, expecially if its business as its rather unprofessional, to me anyway. How old is she?
He could have met her for lunch and " networked" but he decided a lovely dinner out would be nicer, presumably. He had a chance to say no, lunch is better as I have a family.
Personally I would struggle with being at home alone every night whilst my dh lived it up in London after work. Once a week maybe at a proper event, but not dinner a deux with other women when he should want to be at home with you.
Does he get home late Friday too? Where does he live during the week, does he come home? Or return late Friday?
Quality of time and not quality is bollocks anyway. Does he spend the weeks romancing you and being a great dad? Then disappears for the week again? Is he a bit possessive of his phone?