All my Dads contacts have been synced onto my phone?

Me and my dad both share the same iTunes account, but sync our iphones on different computers.

But today all of his contacts appeared onto my contacts (there's about 1,400 contacts) and everytime I delete one, they get deleted on his phone too.

So I made a new iTunes account but didn't want to restore my phone as I have made lots of purchases on my dads iTunes and if I restore it, i could lose them all. All the contacts are still there and I want to get rid of them.

Also, I tried syncing my phone onto my Mac and tranferring all my purchases but it only transferred the latest ones (the ones I purchased in the last week) and not the ones from since I had the phone.

What could I do?

😕

Help!