Current protection order against my EstrangedHusband; he can't/won't comm. filing of dep. children w/me..? I have FullCustody; they visit him 8 hrs/wk (same all of 2022).

The IRS will  not tell you if someone claimed your children.  If you try to e-file and the e-file is rejected for duplicate use of SSN's that will be your big clue that your ex claimed them and filed first.  If that happens, your only recourse will be to file your return claiming the children by mail.  The IRS will process your return and later they will sort out the duplicate use of the SSN's.   Your ex may be subject to repayment of any refund he got as well as penalties.

When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s.  Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.

Federal and state returns must be in separate envelopes and they are mailed to different addresses.  Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.

And...

https://ttlc.intuit.com/questions/1900655-what-to-do-if-you-suspect-tax-related-identity-theft

Most important) Follow the IRS procedures for reporting a fraudulent return, documented here: www.irs.gov/uac/Taxpayer-Guide-to-Identity-Theft

IRS INFORMATION REFERRAL TO REPORT VIOLATION OF TAX LAW

https://www.irs.gov/pub/irs-pdf/f3949a.pdf

If your Social Security number is compromised and you know or suspect you are a victim of tax-related identity theft, take these additional steps:

• Respond immediately to any IRS notice; call the number provided.
• Complete IRS Form 14039, Identity Theft Affidavit. Then print and mail or fax according to the instructions. 
• Continue to pay your taxes and file your tax return, even if you must do so by paper.

6-digit IP NUMBER FROM IRS

https://content.govdelivery.com/accounts/USIRS/bulletins/2af48f0?reqfrom=share