Shot placement
Be sure to aim for the shoulders or between neck and shoulders if you can't get a headshot.
The dogs have already demonstrated they are a threat to other companion animals (****er spaniel)--it won't take much for them to attack a human.
If they are on your property, without your permission and the "owners" nowhere in sight (to recall the dogs)--keep firing/reloading until the threat is stopped.
As I am not familiar with TX law (IANAL) IRT pets as property, I would much rather deal with a property charge vs hospital stay, medical bills, physical therapy, etc. If these pet owners were responsible, they would ensure the pets stayed on their property, especially since you have already informed them of dog's behavior.
My son was bit by our neighor's dog and now has scars all over his head--this was an unprovoked attack, so I can sympathize. According to VA law and local statute, I am permitted to use the necessary force to defend my family and property (my dog) from the neighbor's dog, should he be found on my property. My necessary force is 165grains of jacketed-hollowpoint love.
Good luck