Thoughts (which are by no means to be taken as legal advice) ...
Almost without exception, from the "Duty to Retreat" statutes I have seen, the requirement is to recognize the duty to retreat/disengage if you are able to do so. None of them are absolute, blind to conditions.
If by "Permian Basin" you mean Texas, then check the TX Penal Code, notably Sec 9.31 Self Defense and Sec 9.32 Deadly Force in Defense of a Person.
The WHOLE reading of 9.31, 9.32 and 9.33 (among the other statutes) is important, of course, and all of it applies to you. But, note specifically the language in 9.31(e) and 9.32(c) regarding your right to use reasonable force in a place you have every right to be.
According to 9.31 Self Defense:
According to 9.32 Deadly Force in Defense of a Person:
9.31(e) A person who has a right to be present at the location where the force is used, who has not provoked the person against whom the force is used, and who is not engaged in criminal activity at the time the force is used is not required to retreat before using force as described by this section.
As well, note that 9.32 Deadly Force in Defense of a Person states that:
9.32(c) A person who has a right to be present at the location where the deadly force is used, who has not provoked the person against whom the deadly force is used, and who is not engaged in criminal activity at the time the deadly force is used is not required to retreat before using deadly force as described by this section.
... in which the actions taken are presumed reasonable in cases of protecting against use or attempted use of unlawful deadly force, or the imminent commission of aggravated kidnapping, murder, sexual assault, aggravated sexual assault, robbery, or aggravated robbery.
9.32(d) For purposes of Subsection (a)(2), in determining whether an actor described by Subsection (c) reasonably believed that the use of deadly force was necessary, a finder of fact may not consider whether the actor failed to retreat.
It might not always be possible to safely or effectively withdraw or retreat. Imagine your child has been taken down and requires your assistance and/or defense; or, if you're disabled; or, if retreating would mean all-but-certain death or crippling harm being done to you. NOTHING in these statutes requires you to retreat at all costs. And these statutes specifically acknowledge that in such cases of violent crime being done upon you, there is a presumption of reasonableness and acknowledgement of no duty to retreat in such circumstances.
The duty to retreat if able (given the sanctity of life) is acknowledged in the statutes, sure. But the right of the citizen to use the degree of force one deems reasonably necessary in the circumstances is also strongly supported via these statutes. And the circumstances any person is faced with always must include the totality of circumstances, and that includes any disabling physical issue that precludes safe withdrawal, any situation at the scene that precludes withdrawal (ie, needing to stay with a downed child or other person who requires your assistance to avoid death/injury).
Most of it basically comes down to reasonableness. If 90yrs of age and infirm, or if medically disabled or limited in one's ability to effectively flee or resist, it should be clear the statutes allow for these variations in the population. Not everyone's an athletic and fit 6'4" with deadly and subtle hands and able to run like the wind. Some people have very reasonable physical limitations that preclude any retreat, protracted resistance or ability to withstand larger and more-aggressive assailants.
The point of all this is: you're the citizen. You have every right to determine on your own what you deem to be reasonable in that situation, subject to the right of all other citizens in your state to judge that reasonableness after the fact.
Still, it's always in our best interests to be seen as the one who's attacked, under threat, instead of the aggressor. Not provoking or instigating the confrontation, backing up, speaking your intent to not harm anyone, speaking your intent to avoid confrontation, loudly demanding you be left alone, loudly asking others for help/911, staying behind cover/barriers if able, and firmly resisting any attempt to damage you (even if that takes deadly force to do so). All of these aspects can help your case, in such a situation. It'll still be up to a jury of others to determine the reasonableness; no avoiding that. As such, everything you can do to help assure your actions are seen as reasonable is in your best interest, presuming you're safely able to do such things ... and that includes retreat.
For myself, what would I deem reasonable? I'm disabled, not able to run any great distance, and not able to withstand a violent and determined physical attack for long. I'm all for withdrawing if safely able to do so, but not at the cost of my life or the life of another. If attacked, I'll defend against it. If the assailant's actions require a level of force sufficient to stop those actions to a degree that appalls people, so be it, so long as I believe that level of resistance required to stop the attack. And that's the crux of the "reasonable man" and "duty to retreat" elements in the law. As with anyone involved in any such situation, I'll be on the hook to have my actions adjudged by others for their reasonableness and justifiability. I'm willing to stand for that, as I should be, since I believe such actions to be lawful, right and just, and all such actions of a criminal violent assailant to be the opposite. But that's just me.
If you're still concerned over the use-of-force statutes, I would strongly suggest speaking with a competent attorney in your state who is well-versed in this subject.