This is super interesting. I have very similar requirements for two of my modal windows. Also one should also show tutorial video and another should have full screen size.
I have not found which monitor is current active one where dialog is shown in core.getDisplayConfiguration({});. Do you have a solution here?
Also I am wondering if you publish your plugin in CC? As far I know such dialogs are not allowed and it should be refused. See my threat here: Style guide?
“So a modal dialog needs always 40px padding, and dialog buttons at the bottom” otherwise these will not be approved.