To get primary custody of the kids you need to be the "primary caregiver". If your wife is too lazy to get them ready for school, bathe them, etc, then you stand a decent shot at primary custody. Also, if the kids are 12-14 year old range, the judge will give considerable weight to their testimony, if you force them to choose. I didn't want to put my children through that (and they were too young, so the judge wouldn't have given their decision much weight).
Child support amounts in Texas are basically a published rate sheet based on your income and the number of kids. You can probably Google it.
If your wife and her BECAUSE lawyer acts so irresponsible to reject reasonable settlement offers