You're fine with the test kit you have.
FWIW
.03 mg/l is the minimum threshold level to prevent phosphorus limitation in corals, identified by researchers at Southampton University in England using corals maintained in an aquarium for about a decade. .3 mg/l is what corals are subjected to with upwelling in the ocean.
.5 mg/l might be acceptable for some as acros have been shown to increase growth up to this level.
.9mg/l is the level the Steinhart Aqaurium's ex situ sexually reproduced acro colonies are being grwon out with. Rich Ross's (who's part of the team at Steinhart) has his acro dominate mixed reef sitting at 1.8 mg/l, his tank can be seen at the beginning of his
MACNA presentation on phosphate. You can see his current levels as well as some cool videos of corals spawning in his thread.
This tank was built before r2r, here is a link to some links about the build. http://packedhead.net/home-reef/ Current test results: 03-17-2017 Ammonia (NH3-4) Good 0 0.000 - 0.050 mg/L 03-17-2017 Nitrite (NO2) Good 0.006 0.000 - 0.100 mg/L 03-17-2017 Phosphate...
www.reef2reef.com