I am not sure why you would see OnlyFans as a way to get people to a dating site.
One thing to think about is by setting your site to just Sweden, you are limiting your customers to just Sweden.
Another point is that while dating sites were huge, becase of data hacks and the fact that we now have large and well known dating apps, I think dating websites are much harder to convert.
Anyway, some ideas:
1. Facebook - Target people by age and country.
2.
Plugrush - Cheap traffic that you can select by country and so on.
3. YouTube adverts.
4. Twitter - make sure you have a twitter account.
By the way, if the only females are onlyfans models on your site, I would presume you have not many ladies on the site, unless some profiles are fake.