Soup helped me a great deal on my vlcd. I would chop asparagus up really small and boil it in my chicken broth/water mixture then add grilled chicken, everything chopped super small. I recently found out though that even though original protocol allows salt-THAT MUCH salt is not good. At all. Even the low sodium stuff still has a lot. So I would say no on the broth unfortunatley
As for measuring lettuce, the difference between a packed cup and a loose cup is about 5-10 cals so I wouldnt worry about it.