1) it's possible to merge files by importing the tables, scripts etc but it's a fair amount of work and failure to do certain steps just right can tie you up with bugs until you figure out what's broken. THere's a third party product I've heard of: FMMigrator, that is supposed to make this easier thought I haven't used it. If you haver just one or two tables and just a few scripts, value lists and layouts in the file you want to merge, it's not too bad, otherwise, be prepared to invest a great deal of time and effort doing this.
You may find it easier just keeping the files separate and linking the tables of one file as external data sources of the other. This can enable you to add a box on your relationship graph for a table in an external file so you can relate it to your other tables and access the data just as though it were in the same file.
2) That's a pretty vague description, but if you use a field in the ticket record to store an account name or even an actual name, you can use finds or portals to just display records that apply to a given person.