Section 302 of The Veterans Benefits and Transition Act of 2018 ("VBTA") changed the law so that, if an active duty servicemember is a legal resident of a particular state for tax purposes, the spouse can unilaterally elect to also be a resident of that same state. The factors previously used to determine the spouse's legal residence, such as the spouse's physical presence in a particular state or the identity of the state in which the spouse maintains a driver's license, vehicle or voter registrations, or professional licenses are no longer relevant.
See Section c (3) of this reference:
https://www.jag.navy.mil/legal_services/documents/Info_Paper_2018_SCRA_Amendments.pdf
Therefore you have the option of electing to be a resident of TX for tax purposes. You do not have to file an Illinois return.
Here's the actual text of the law (see Section 302):
https://www.congress.gov/bill/115th-congress/senate-bill/2248/text
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
