Tossup/Tilt D (slightly). It should be noted that O'Rourke was not the only statewide Democrat to win this district (the Democratic AG nominee won it as well), and it was fairly close at the House level despite not being seriously contested. This is probably the most likely Texas to flip after TX-23.
So 2 Dems winning it (out of 8? statewide candidates) makes it Tilt D? Tilt R imo for sure, though it's basically a meaningless distinction
Since it takes a bit for downballot voting patterns to match up ticket races like President and Congress, yes, the fact that this seat voted for the Democrat for AG despite Paxton being from DFW is a pretty big sign
I just love how you keep assuming 2020 will have a similar national environment as 2018 when it very likely will not