I don't know for sure, but could #4 be Johnson grass? It kind of looks like it. . .to me anyway.

Definitely King Ranch bluestem (Botriochloa ischaemum). It's very common in central Texas and is considered invasive. I've never actually seen big bluestem while living in central Texas but it's supposed to grow in tight clumps whereas KR bluestem blankets roadsides and fields. You'll know little bluestem by its steely blue color when alive and strong vertical growth when going into bloom.

Festival rubra is probably the fastest to fill in, but will definitely need more frequent mowing than Carex spp's . I've found that Carex praegacilis can have winter dieback when it has to deal with wet clay and little winter sun. Carex pansa is taking a very long time to really fill in in my first application, the lawn is almost 10 months along and still has lots of gaps, I had planted it at about 5 inches on center. In my opinion, Carex divulsa has proven to be the most adaptable, fastest to fill in and most drought tolerant as well as wet feet tolerant of them all. I intend to stick with C.divulsa from now on, although I haven't tried Festuca rubra by itself. If you don't get hung up on the true "California native" pedigree, Berkeley Sedge makes a great lawn with great wear qualities and superior drought and winter performance that the others don't measure up to. If a usable lawn requiring less frequent mowing and just once a month watering is the primary criteria, I'd suggest you get over being a purist about the provenance. The various lawns of each that I've installed are all in the backyards, so not visible from the street. You'll need to address the Oxalis issue first, unless you don't mind the mingling.

wouldn't it be easier to pull up a clump and transplant? i don't know for sure but, based on where i see it growing, it doesn't appear to be a plant that needs much pampering. it could also be that it only grows where it wants to grow! i just happened to notice large stands of it behind our office building this morning and took this photo. it appears to be the same species to my untrained eyes and i also find it attractive as it sways in the breeze. these are growing on poor, rocky soil at the edge of the parking lot. full sun and not what i would call moist soil. it may get some water seeping from the edge of the pavement and surface runoff during rain events but, other than that, it is a hot and dry spot. broom sedge would be an appropriate name, rhizo. i remember watching my elderly neighbor gather the stems, shape with a machete-like knife (cutting off the ends with seeds) and then tie the bundle with cordage. she used it like an over-sized wisk broom on her back porch.