What's your question? Ask

These articles should help: https://www.gardeningknowhow.com/edible/fruits/blackberries/growing-blackberry-bushes.htm

https://www.arborday.org/trees/fruit/care-blackberry.cfm

This article should help: https://www.gardeningknowhow.com/edible/fruits/blackberries/blackberry-pruning.htm

It is recommended that you prune lateral tips back in the spring. How much is a point of discussion, with some sources recommending to tip to 18 inches and others suggest cutting them back by 1/3 to 1/2.

I would not recommend pruning them now. They will be in their dormant stage now and pruning them may bring them out of their dormancy. If they come out of their dormancy, they will have no protection from the cold and will suffer damage that they would not normally suffer.

I would recommend waiting until early spring to prune.

Almost all weed killers have a period of time after which where it is safe eat food grown in them. The time varies. Since this has been ongoing for 3 years, the soil may still have remnants of the chemicals used. After about a year without the use of any chemical control, however, it should be ok. As a precaution though, I would suggest washing the fruit thoroughly prior to eating it. Here is more info: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/how-long-does-weed-killer-last-in-the-soil.htm

Brazos blackberry (Rosaceae 'Brazos') is supposed to be the easiest blackberry to grow in the Houston area, but its seeds can get quite large. While it doesn't grow as elaborate as the Brazos variety, Rosborough blackberries (Rosaceae 'Rosborough') are another highly recommended type that is suitable for your area and has much smaller smaller seeds. Here is an article that you may find helpful: https://www.gardeningknowhow.com/edible/fruits/blackberries/growing-blackberry-bushes.htm