No way to tell how rich your compost tea is, unless you know somebody with a chem lab? But it still would vary with each batch, according to how much and what was in the compost and how much you diluted it.
You might designate one plant as a test subject to see if, and how much you need to dilute the compost tea. It's probably not high in nitrogen in any case because nitrogen is used in the composting process. Supplementing with the cheap lawn fert is going to be your best bet for keeping your veggies fed, I'm afraid.
Soil testing is pretty variable, too and as somebody said above, the nitrogen is so soluble, the reading would vary from place to place in your garden, and also by season. In spring when the soil has been 'resting' all winter and you've been amending with your compost, it might have a higher N component than after you've been watering all summer, or even after a few heavy rains that would wash/leach out all the soluble components.
Have you considered planting a cover crop of some legume? They 'fix' nitrogen in the soil, I forget how it works, though. Anyway, you plant something like vetch or cow peas, let them grow a month or two, then till them under and plant your spring garden. I think organic farmers use this system to renew their soil, planting the cover crop in fall after the main crop is harvested.
