You're most welcome. It is possible to transfer to Balmung (I know that for a fact as I transferred there myself from Ridill back at the end of 2014), but I think there are times when even transfers are locked. So if you want to transfer to it it's best to try during it's 'quiet time' which is early/mid morning US time, seeing as it's a US server and thus most of it's players would be either in bed asleep or at work or school.

And yes, PC and PS3/PS4 players all play together on the same servers, servers are only grouped by 'data centre' which are arbitrary groups designed to reduce congestion during patches. They are also listed under their physical location (Japan, North America and Europe), but again there is no restriction to playing a server that is not in your actual region - a US player can freely play on a JP server for instance.