Yes, you have to go through version 11 to get to version 14. No, you don't have to upgrade your server, or even all the clients. You just need one copy of version 11 to do the conversion from .fp5 to .fp7. You can then proceed with the next conversion to .fmp12 through version 14 (which everyone, server included, will need).
As to your question regarding missing data, it sounds like either there's a relationship that's broken or the lookups (perhaps?) that are supposed to populate the name and address information have been tampered with. It could be that, since this is showing up when you enter a new record, that that proper key field isn't being inserted either in the file you're working in or in the file you're attempting to read data from. That's the first place I would look.
Thank you. I will see if I can find it. It's hard not knowing the program that well.