Yes, it's definitely 'he opened' (διήνοιξεν being 3rd person, singular).
That's correct. I somehow have lots of modules in Accordance called LXX-something.... but I don't know the history of them and didn't realize there was a difference (in the Greek).
Think most of Accordance's (and Logos') LXX modules are based of Swete's LXX.
Unless of course it specifies as being from Rahlfs -
https://www.logos.com/product/7080/sept ... morphology
Interestingly, in Swete's apparatus, he doesn't list διήνοιξα as a variant reading in Ezek 3:2.
Why is this version different to the others?
Swete uses Codex Vaticanus (IIRC) as his main text, and so is just reproducing a transcription of that in his LXX version (with missing sections provided by Codex Alexandrinus).
NETS as been noted, is based on the full Gottenburg critical edition.