Is it proper to charge a Defendant in Texas with Continuous Family Violence (2 assaults w/in 12 month period) if one of the assaults is alleged to have happened in another State?

My thought would be no. The statute says engages in conduct that constitutes an offense under 22.01(a)(1). The CCA recently addressed this issue regarding continuous sexual abuse of a child in Lee V. State PD-0880-16(opinion issued on 10/4/17). I would read Lee, although the language of the statutes are slightly different I think the same analysis would apply and that both assaults must take place within Texas.

That was absolutely my concern following the opinion in Lee. Thanks.

Yeah, I'd agree. You could definitely introduce evidence of the out-of-state assault, but your jurisdictional two assaults would need to be within Texas under Lee.