it keeps saying that there's an error exporting my start date and thats the last thing i have to change, i've tried overhauling and everything. how do i fix this..?

Is the error you're seeing this one:
Unable to create country as mod has start date overhaul set, but no start dates could be found

This error is only meant to show when creating a new country when you have set "Start date overhaul" on your mod, not created a start date, and then tried to create a country. Not too sure why it was doing this check if you weren't trying to create a country - but this should now be resolved.

As for the error itself, you will need to create a start date if you are looking to create another country/assign it to your existing country, or disable the "Start date overhaul" on your mod, and edit the start date in later. Setting this checkbox disables the default start dates, and countries' data gets assigned to their start dates... so if your mod doesn't have a start date, it can't create a new country as it wouldn't have any date to assign the data to.

it says "errorexportingmodstartdate" which is the one descriptor file i'm missing for my mod

ill try the method you've explained.