In an effort to fine-tune the timeline:
Saturday 9/2: LW texts sister re "adventure in the country", likely during the day or early evening. She and TT later go to the grocery store, return to her condo, unload groceries, and walk the dog. He leaves in his own vehicle, she leaves in her Ford Escape a short time later. Neighbors report that her vehicle is not seen in development after this time.
Sunday 9/3: LE speculates that this is the date that LW is murdered. Sister reports no contact from her and that family cannot reach her. TT texts friend for late-night ride to Baltimore which is declined. It is either this day or 9/4 that TT ditches her Escape in Columbia, pulls front tag, throws DL and phone into dumpster and gets ride from female friend who he later asks to deny this to LE.
Monday 9/4: TT tells LE that this was the day of early morning fight (LW hysterically crying and demanding house key). Also claims that he requested a public meeting at Columbia Mall. Tells LE she never showed and he drove by her condo, but did not enter b/c he no longer had a key. Neighbor tells LE that TT was seen in afternoon walking the dog. Dog was found by LW family that evening in locked condo.
Tues 9/5 thru Mon 9/11: TT spins tales of showing LW property for house; visting property repeatedly looking for LW; being told he's not the father, giving LW time to sort out thing, etc. etc. etc.
I agree with the previous poster who thinks that TT intended to kill her on 9/2 but couldn't because of texts to her sister. At some point on 9/3 he did murder her, probably after securing her phone. That would explain all of his clean-up efforts and lame-*advertiser censored* excuses about subsequent events.
Again, this is the exact situation where the DP is justified.