Schengen ban-solutions

[Italo]

Hello all,
I really need your help.
I am an Italian living and working in Finland.
My non-EU boyfriend was denied a residence permit for study purposes (in finland) and deemed a threat to public order with consequences of 4 years Schengen ban.
If he leaves the country voluntary what are chances that the ban will be issued?
Will he be able to come to Schengen countries if we are married?
Can we live together in UK?

Thanks for your time

Regards

[secret.simon]

My non-EU boyfriend was denied a residence permit for study purposes (in finland) and deemed a threat to public order

Why was he deemed a threat to public order?