If your husband lives in Texas, that state has jurisdiction to grant a divorce. (It may not be able to do more than that - as you note, it has no jurisdiction over custody or child support issues - but it can grant the divorce itself.)

I have no way of knowing the status of the Texas case, or why it hasn't been resolved. If your German lawyer can't help and the German court won't help, maybe it is time to consider hiring a Texas family lawyer to try to wrap things up in that state.