The specific assault charge would be defined by the criminal statutes of Texas. Yoru question is vague on the most important details - all that stuff about what she's doing for him, that's all irrelevant.
Depending on the severity of injury, or if he used a weapon, this could either be a misdemeanor or a felony in NYS.
"She tried to drop the charges"
Charges are not pressed or dropped by private citizens, even the principal victim.
"His bail is $10,500 which according to him is over $8,000 more than the other people in there charged with the same thing."
Bail isn't based entirely (or even principally) on the nature of the crime, but the record of the defendant. His is probably noteworthy enough.
"I want him to stay in jail as long as possible"
This probably won't be long if the victim doesn't cooperate.
Unless there are other witnesses to what happened, unless she cooperates, the case will probably crumble.
If she reported the crime immediately, anybody who spoke to her about the facts of the case in the immediate aftermath of the incident may be able to testify as to what she said. Statements made outside of court are typically inadmissible when used to "prove" the substance of those statements. An exception to that rule (unsurprisingly used in domestic violence cases) involves "excited utterances" - statements made out of court about an incident that had just happened. There is no specific time limit as to how immediate the statement must be made, but it must be made while that witness is still under the emotional stress of the incident. (Just because it's admissible doesn't prove it's true - that's still a jury question.)