Ask Mr. Smarty Plants

1.  Since you have a cement bottom in your pond, your plants will need to be in pots weighted with heavy stones and clay soil that will stay put.  You can cover the soil with pebbles to keep it in place—regular potting soil will mostly float away.  You can use pots of any size or shape and as many as you want. 

Here are some native aquatics that do well in ponds:

Pontederia cordata (Pickerelweed) will have lots of blooms and can grow to 3 feet.

Equisetum hyemale (Horsetail) will grow well, but it will be good that you will have it in a pot since it tends to take over if it isn't contained.

Hymenocallis liriosme (Spider lily)

Marsilea macropoda (Bigfoot water clover)

Kosteletzkya virginica (Virginia saltmarsh mallow)

In saturated soil near the edge of the pond you can grow such things as:

Rhynchospora colorata (Starrush whitetop)

Adiantum capillus-veneris (Southern maidenhair fern)

Canna glauca (Water canna)

2.  Sedges grow well in part shade and their fibrous root system will help stop erosion.  You can buy them potted and divide the plants to insert in the soil at intervals over the area.  They will eventually spread and cover the area.  Here are several possibilities:

Carex cherokeensis (Cherokee sedge)

Carex planostachys (Cedar sedge)

Carex texensis (Texas sedge)

3.  This is a tough question to answer because I don't know what size plants you want or if you want herbaceous or woody plants.   I am going to refer you to the Recommended–Central Texas page.  You can use the different options under NARROW YOUR SEARCH to find something for your site.  I chose "Herb" under General Description, "Perennial" and Lifespan, "Sun" under Light Requirement, and "Dry" under Soil Moisture and found these among the results:

Asclepias asperula (Spider milkweed)

Glandularia bipinnatifida var. bipinnatifida (Prairie verbena)

Melampodium leucanthum (Blackfoot daisy)

Oenothera speciosa (Pink evening primrose)

You can change the criteria and find other possibilities.