My understanding of PBIT files is that you have now created a version of your report that does not have a datamodel included (which is why you were able to save it) - I believe your measures will have saved, but not the data structure.
And with that understanding, I don’t see how you will be able to publish it to the service and have it be useful.
- https://www.datavizioner.com/blog/pbit-vs-pbix-how-and-why-theyre-different/
- https://www.powerbitutorial.org/tutorials/power-bi-templates/
- https://powerbi.microsoft.com/en-us/blog/deep-dive-into-query-parameters-and-power-bi-templates/
You probably need to focus some time on optimizing your data model
@Harsh has recently shared some great resources on this topic: How to speed up Power BI reports for opening and refreshing? - #3 by Harsh