You can expect that the offer will be vary low. I cannot determine what your case may be worth, from a question posted here. I would consult with a local personal injury attorney to go over the details.
You are just going to have to get a lawyer. There is nothing else you can do to make them respond. You might have some trouble finding someone who is willing to get involved at this point, but keep looking, you will find someone.
Send a certified letter saying you do not have the documents if the subpoena is only for the documents. BUT IF THE SUBPOENA ALSO SAYS YOU MUST APPEAR IN COURT OR FOR A DEPOSITION, THEN YOU MUST GO IN PERSON.
How bizarre!! You may have a claim, but the question will be whether there are any damages in addition to the property damage. It does not sound like there are any. There are always two questions in a lawsuit: are they responsible, and if so, how much were the damages.
Wills are not expensive, and a letter is much more difficult to deal with. So get a will. Don't go half way when your kids are at stake. Texas has very modern and streamlined will probate, so the things you may have heard in the past, don't apply in Texas. It is easy. All sorts of things can go wrong if it is just a letter.
He has a workers compensation claim and may have a third party personal injury claim. He should hire a personal injury lawyer to handle his case. He should not talk to the other sides insurance company until he talks to a lawyer.
Without an attorney you can expect to either have the claim denied or a low ball offer. You can hire an attorney on a percent fee, and the attorney will do the negotiating. The delay in treatment will be an excuse the insurance company will use to deny the claim, but a lawyer will know how to respond.
DO NOT SIGN!! There is no such law. Your husband should also not sign until you have at least talked to a lawyer. If the settlement is OK, the lawyer will tell your husband how to handle the release. The fact that your husband returned to work may or may not mean the settlement he is being offered is good. Talk to a lawyer board certified in personal injury law by the official Texas agency--the Texas Board of Legal Specialization. Look at my profile and call my office for an appointment....