You don't have any options other than to stick it out until it's repaired.
Section 92.052 of the Texas L-T Act requires that a landlord "provide and maintain in good operating condition a device to supply hot water of a minimum temperature of 120 degrees Fahrenheit" and "make a diligent effort to repair or remedy a condition." That section, unfortunately, doesn't give you a remedy if he fails to repair it.
Section 92.056 does give you remedies for a condition that "materially affects the physical health or safety of an ordinary tenant." A non-working water heater does not a health and safety issue because you can heat water on the stove for cooking, washing, bathing, etc. Inconvenient, yes, but nothing for which you can break your lease or have the landlord pay for alternate lodging.
https://law.justia.com/codes/texas/2...-8/chapter-92/
Like I said, stick it out until it's repaired. Don't try to fix it yourself or you might end up buying it.