Here is what I suggest. See if you can have a local building inspector look at your premises and the problems you have and see if there is a code violation. A code violation will help you greatly for the end game to this situation. Next you should make sure you put in writing to the landlord the history of the complaints you filed with them related to the problems and the neighbors. In that letter that you state that you were constructively evicted for the period of the repairs and owed no rent for that. You also want a rent abatement for all the problems you have identified in the rent and that you want a response from the landlord before the January rent is due. I would send this letter with your Dec. rent payment.
From your post, the landlord is not going to take care of any of the problems. He may not respond.
You can then do one of two things. You can take the landlord to court to recover all your rent for the period you had to vacate for repairs as well as a claim a portion of the rent you have paid during the tenancy because the condition of the apartment was so bad you did not get the full value of your rental payments. You will also seek to recover your moving expenses on the basis that the non renewal of the lease is in retaliation for your complaints. You will also seek one month's rent and $2,000 in damages for the landlord purporting to change his duty to provide a habitable premises in violation of Texas law. Here is a link to a handbook on Tenant's rights in TX and you will the $2,000 mentioned on p. 13.
I also suggest you speak to a local landlord tenant attorney because it may be that you would be entitled to recover attorneys fees and an attorney might take the case on a contingency. Having a code violation would strengthen your case considerably and that is why you should contact the local building inspector.
If you do not want to bring suit, you can refuse to pay Jan rent and let them attempt to evict and then bring as a counterclaim all the defenses about the condition of the apartment. Again, if there is a code violation that will strengthen your case considerably. By the time the eviction winds through the court you will have moved anyway. That is why I would wait to not pay the Jan. rent so if you do not want to take action yourself you do not have to be bothered with litigation during the holidays. All of the above you can do without an attorney.
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