Divorced Dad (50) Moved Into My Mom’s House For “2 Days” Back In March And Never Left. What The Heck Do We Actually Do Now? Location: Texas

Location: Texas
I’m active duty Air Force and stationed out of state, so I’m trying to help my mom from hundreds of miles away.
Back in March, my divorced dad (50) told my mom he was staying at her house for two days because of VA appointments. Four months later, he’s still there.
During that time he changed his mailing address to the house, moved in almost all of his belongings, brought his cat, and now acts like he lives there permanently.
This is not something my mom agreed to. She’s told him to leave more times than I can count.
The part that makes me the most angry is that this isn’t even the first time he’s tried this. He’s slowly inserted himself back into the house before, but when I still lived at home I pushed back hard enough that he eventually left. I genuinely think he waited until I enlisted and moved away because he knew my mom would be by herself.
The frustrating thing is he has options.
He receives roughly $2,000/month in military retirement. He substituted during the school year but hasn’t worked since summer started. He keeps saying he’ll “find a job soon,” but that’s been the excuse for months.
His own family has offered to help him get an apartment. They’ve offered to help him move. They’ve tried talking sense into him. He refuses all of it.
Meanwhile, while living in my mom’s house for free, he paid off his car and even bragged about it.
Living with him has become miserable.
Security cameras show him going in and out of the house well over 100 times a day. He’s already broken a lock and jammed the garage opener from constantly using it.
Every single time he goes outside to smoke, he walks through the house turning off every ceiling fan first. We’ve asked him countless times to stop because it makes absolutely no sense and is just one more thing everyone has to deal with. He refuses.
He tells my mom to “shut up,” including in front of guests and her own relatives.
He slaps her butt, demands hugs, and gets offended or accusatory when she tells him no.
He uses the bathroom with the door open, lies naked on beds afterward to “air dry,” doesn’t flush, leaves the toilet seat up, and often doesn’t wash his hands.
He called my sister and me “spoiled brats.” He said it to my face after I came home on leave from training because I told him he shouldn’t tell my mom to shut up after she told him to cover his mouth when coughing.
He expects my younger sister to drive him places despite managing perfectly fine before he moved in.
He also lies about my mom.
He brought his cat when he moved in. One day the cat jumped onto the dining table while my mom was eating, so she pushed it off the table. He immediately started yelling and later told his own brother that she “beats” or “abuses” his cat, which is completely false.
My mom is also a naturalized U.S. citizen, and English isn’t her first language. He knows legal situations intimidate her and has even threatened that he could somehow get her citizenship taken away. As far as I know that’s complete bullshit, but it scares her because she doesn’t know what rights she actually has.
After months of begging, I finally convinced my mom to contact my dad’s family instead of trying to deal with this alone.
To their credit, they’ve been trying to help. They’ve talked to him repeatedly, offered to help him find an apartment, and they’re sending my mom an eviction notice template to serve him. They may even come down in about a month if this still isn’t resolved.
The problem is that he simply refuses to leave.
We also finally located the divorce decree. The court awarded the house to my mom in the property division. His name is still on the mortgage though.
And this is where my frustration shifts toward my mom a little too. I understand why she’s overwhelmed—English isn’t her first language, she’s intimidated by the legal system, and she’s spent years being manipulated by him—but she also genuinely doesn’t know what rights she has, so she freezes instead of acting. That’s why I’m here trying to figure this out for her. She also relied on me too much to basically deal with him, which as a daughter frustrates me. Their relationship isn’t my issue to resolve/ create boundaries for.

My questions are:
We can’t afford an attorney.
So what can we realistically do ourselves?
Can she file an eviction on her own?
Does the divorce decree make this an ejectment instead?
Does his mailing address change anything legally? Like he’ll be considered squatting so we can’t kick him out?
Are there legal aid organizations that help with situations like this?

I’m honestly just trying to figure out every option we have because I’m tired of watching him manipulate my mom while refusing every reasonable opportunity to leave.
Also my little sister is there for the summer for college break.

Edit: he does pay the water and gas bill and everyone’s phone bill. But that’s not shit