Another difficult one! I can't really advise, but I can tell you what we do - we give parsley, spinach and kale about three times a week and it amounts to about a third of a cupful. We give these size bowls:
the pic was taken back in the days when we had less pigs and considerably more time (and money

|)!) I put in some other items in the pic so you can see how big the bowls are in comparison. They also had a little more cucumber in this pic than they usually have as this was taken two years ago in summer when it was hot. We put in a little more so it's full to the top these days, it works out to around a cupful of veggies when chopped up etc.
I try to avoid too much carrot, I usually put in about two 1cm chunks of an average sized carrot per pig about every other day, I try to alternate every other day.
I give broccoli occasionally but not too much as I read that that and cabbage can cause bloat so that's a treat, but they love it. I never feed cabbage, only greens.
The Ca/ph issue is a tricky one and I try to not let it drive me to distraction, so I try and stick to what I said before about high Ca foods being fed no more than 4 times a week, usually three.
If it helps, I feed this:
Most days:
Greens
Celery
Cucumber
Coriander
Peppers (pref green)
Every other day roughly:
Carrot
Baby corn
French beans
Dill (if we have any in)
One cherry tomato (**** a bit less than every other day)
Three times a week or less/treats:
Spinach
Romaine / Little Gem lettuce
Kale
Parsley
Broccoli
I've probably missed some out as it's a bit early!
That hasn't really answered your question, sorry
