Charged with Assault with Bodily Injuries in Texas- Need Guidance on Police Contact and Legal Steps. 1st time offense.

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Hi, I’m seeking legal advice regarding a recent charge I received in Texas. I want to handle this responsibly but am unsure of the best steps.
Location: Austin, Texas.

Timeline of Events:
I had an altercation with my ex. It was a mutual combat situation, though he initiated the confrontation and I acted in self-defense.

The next day, he went to the hospital for military-related reasons (he was considered AWOL and needed documentation to travel). I was not involved in any report at that time; the hospital made a report based on his account. He initially did not want to involve me due to the unfairness of what he started and continue the relationship (wanting me to live with him/ staying in contact/meeting up with me etc.)

About a month later, after we broke up, he named me in a statement. Clearly out of spite.

Recent Police Contact:
Officers called me via private/no caller ID, yesterday, saying they wanted to hear my side and requested an address to meet. I wasn’t in the city or at my residence and suggested a better time. They said they would call next week.
But later, they went to the residence. I am not on the lease so my residence is at my friend’s. My ex knew where I was staying at, so he clearly told them where I could be. My friend answered the door, said I wasn’t there, and was given a number for me to call.
Today, a detective called me at 9:30PM but I was asleep, then my roommate called me saying he contacted her twice wanting to speak with me and said they plan to show up at the apartment again. My roommate does not want to be involved and expressed that to them.

Additional Information:
I am not trying to avoid the police. I was initially hesitant because I’ve received calls from my ex through no caller ID.
I cannot currently afford a lawyer.
I am considering self-surrender. This is my first offense.
I have video evidence of my injuries from the night of the incident but did not go to the hospital.

Questions:
Can I prevent police from going to my current residence?
What are my rights if I want to give a statement?
Am I allowed to have a court appointed lawyer before I say anything?
How does “self-surrender” work, and how does it differ from pleading guilty or entering a “no contest” plea?
Is it common for police to act as though they want to hear your side while actually using tactics to pressure you and arrest you?
What’s the best and worst case scenario?