My two cents on THEO:
I think they got together while/after filming ISTL. But something happened around the end of July / August and they either split or took a break: they seemingly spent the whole month of August apart and they were acting quite distant at TIFF, even at the premiere when they did not know yet that ISTL was a flop. When asked about the relationship, they denied it since they were not together anymore. (Sidenote: EO might have held hands with MA to make TH jealous?)
Then I think they got back together (maybe in early October when she was supposedly seen in London after her stay in Paris?), which would explain their lovey-dovey body language at the Nashville premiere and the latest sightings of them together.
This is just speculation on my part.