How can I replace my primary url globally with a parked one?

Ok so long story short, someone on our team accidentally got the domain we wanted booked on wordpress.com and not with a host for wordpress. ooopssss

We’ve got a slightly inferior domain booked with a host now, and we’ve got the superior domain parked on that host now. Good, right? you can follow either url to our site and it works.

So let’s say:
Superior domain: example.com
Inferior domain: ex-ample.com
Get the picture?

PROBLEM: all the links in the site still direct to a url with a base of ex-ample.com, even though we want someone visiting the site to only be visiting pages headed with example.com. I hope I’m explaining myself well. once we get to http://ex-ample.com/page/subpage, we can remove the dash and it still works. but aesthetically, it’s really unfortunate, and I want clicking the link that leads to /page/subpage to automatically be http://example.com/page/subpage.

I feel like we could solve this by changing the home URL. I already followed instructions to change the site URL, but it seems that if we changed the HOME URL to our parked domain, the site breaks and directs to an ad-supported landing page about gardening. I’ve used FTP a couple times to reset both urls to ex-ample.com and try again, but it turns out it will only let us change the site url and not the home url, which doesn’t really help us much anyway. I’m wondering if there’s some kind of workaround to make a function that uses an alternate home_url() or something. any ideas?

thanks so much

Ben