Hi Keith,
You have a favorable tvfool map to work with.
An Antennacraft HBU22 would work fine for your situation. It's not a beast of an antenna by any means. Orientate to magnetic heading 175. Make sure to have as clear pathway as possible to the south. If you are shooting through trees, reliable reception may be more problematic.
You should be able to find an antenna chimney mount:
http://www.homedepot.com/p/Channel-M...3080/203763048
Then a 5 or 10' 1 1/4 inch pole from your local homedepot or super hardware store equivalent ought to do the trick.
How many TVs do you intend to serve? Four? If so you may need a distribution amp. (
http://www.channelmasterstore.com/TV...fiers_s/40.htm)
As for you direct TV equipment, generally the coax can be repurposed. The splitters though it's best to remove all the direct TV installed splitters and install ones you know are compatible with over the air TV.
I would expect with the HBU22 aimed to magnetic 175 with no trees or other obstructions you would see the big 5 plus the majority of Houston TV broadcasts. You may also see KBTX CBS off the back from College Station.
Cheers.