Angels will like your water, but please, not in a 14g tank. I was going to suggest you read the profile on Angelfish to learn their tank requirements, etc., but just noticed it is not complete; one of the older ones that needs some revision. I'll tend to that later, but for the present a 55g tank is minimum for a small group of angels and they need to be either in a group of as a mated pair.
With hardness numbers like those, I'm wondering if your location "Washington" is Washington state? I'm just north in Vancouver, Canada, and our water in the Pacific Northwest is very soft and slightly acidic, the sort of numbers your fish store gave you. Anyway, they are very soft, so that supports my thinking as to why your pH fell so much so quickly. It would be good to get this number confirmed from your water supply people. You don't need a hardness test kit, once you know the tap water hardness that's it. The others though are good, and API is a good kit. If pH is not included, pick up a normal range pH kit next time; API make normal range and high range, you want the normal.
With a 14g tank of soft water, some lovely fish choices could be the smaller characins (tetra like Ember Tetra, pencilfish, hatchetfish), dwarf rasbora (Boraras species), dwarf Corydoras species, perhaps for a single specimen fish something like a small gourami (honey gourami would be best), one of the dwarf SA cichlids like the Checkerboard, etc. All of these would do well with some wood and live plants. Leave the coral out, it will harden the water.
White clouds are OK with your water, and they are nice fish; but like all shoaling fish they must be in a group of 6 minimum, which takes up a lot of the available water space in a small tank. So you might like to browse the profiles before deciding on more. Also, they are cooler water, and fare better at room temp (around 70F) so this can limit tankmates as most tropicals are warmer water. This fish is also in our profiles, White Cloud Mountain Minnow. You can click the shaded name of a fish species to see its profile, or click the second tab from the left in the blue bar across the top. All the fish I've mentioned above are in one of characins, cyprinids, or catfish; the gourami is anabantid, the cichlid obviously cichlids, but this one is not there (yet).