Dear Georgina,
You must be tired!
Reading your essay I am struck by the number of references to 'the uni-temporal Now', which as you observe, Einstein messed up bigly with his multiple-time-based 'relativity of simultaneity' leading to 4D-ontology with no NOW.
I hope you will enjoy my current essay, Deciding on the nature of time and space, which provides strong support for this crucial aspect of your model, and does it based on an argument that also fits with your observation-based model.
I believe this will strengthen your model considerably, since you do appear to need the uni-temporal Now'. Please let me know your opinion.
Best regards,
Edwin Eugene Klingman