I have a defendant charged with intoxication manslaughter and also with intoxicatin assault (two separate victims). Can I give him a TDC sentence on the manslaughter count and a probated sentence on the intoxication assault case to run consecutive to the TDC sentence if the counts are severed into separate criminal cases?

You can stack a probation on a prison sentence. See art. 42.08, CCP. It might take two trials, though, absent the defendant's consent, because he has a right to concurrent sentences for multiple convictions arising from a single trial. See sec. 3.03, PC. The only exceptions are for intoxication manslaughters and certain sex offenses.