Iron - 0.1 ppm
pH - 7.0
Ammonia - 0 ppm
Nitrite - 0 ppm
Nitrate - 2 mg/l (by Profi-Test)
Nitrate - 10 mg/l (by AquaVital Multi-Stick)
KH - 10 degrees
Total Hardness - 120 ppm (AquaLab-1 Stick)
Total Alkalinity - 300 ppm (AquaLab-1 Stick)
Phosphate - 0.03 mg/l (by Profi-Test)

PO4 is too low.
NO3 is likely off. See test kit issue above.
Lamott is good for test kit reference.
Add 1.5 teaspoons of KNO3. This will give you about 6-7ppm of NO3 and
4ppm of K+.

You'll need to remove the Green water and attached algae first though.
You can trim the algae off, add SAE's other herbivores etc, for the
GW, you can use/borrow a diatom filter or a UV sterilizer.
If the GW is mild, try blackout. Cover the tank with blankets/trash
bags etc so that no light at all gets in there. Do this for 3-5 days.
Remove CO2 and add airstones. Add the KNO3 also. Do a 50% water change
before and then add the KNO3. Cover the tank.

Your tank is severaly PO4 limited. PMDD is for limiting, not removing
all of the PO4.
Adding PO4 will increase the NO3 uptake of plants by 500% or more in
such a tank, if your PO4 is correct and it likely is.

Lights - we have power compacts 4 x 96 watt daylight bulbs which figures to
2 watts per gallon. Could it be there aren't enough watts/gallon?

No.

The plants are growing nicely and spreading, but the green water won't seem
to go away and now there is a little thread fuzzies on the Vallisneria and
cryptocorynes again. We change at minimum 50 gallons of water/week.

Any thoughts on why the green water???

See above. Add PO4 and more K.
This is what I'd add to your tank by the week:

Weekly 50% water change.
1.5tsp of KNO3 2x a week
2 teaspoons of K2SO4 after water change.
Trace mix with DI water (2 tablespoons in 500mls of DI water) 35mls 2
x a week.
1/8 teaspoon of K2PO4 2x a week.

NPK and traces. The rest is CO2 and light.
Do that and the tank will grow much better. If the NO3 is low or zero
in between dosings, increase the dosages to 3x a week for the KH2PO4,
KNO3 and traces.

You need to remove the algae first before doing this.
Warning, blackout will make some plants like Gloss very leggy etc.
UV's are very good at getting rid of GW.

Poor plant growth = algae, good plant growth = bad place for algae.
So make the plants grow.

Regards,
Tom Barr