Unfortunately I don't have a good tutorial on this. This needs to be on my TO DO list! There is a bit here:
http://zimpro.co/blog/?p=14 that might help
Essentially once the listings are downloaded you can create and save the database, This is under the menu File item. Once saved, the database can easily be reloaded and, if needed, resynchronized to your shop. A problem I have is the program is evolving. If you hover the mouse over a menu item in many cases it will explain in better detail what the function does, I;ve been adding this with each update,
Your questions on autorenewal and the database are good ones. The database download was designed with the catalog function in mind, not auto-renewal. This is something I will need to look at and get back with you. This weekend is unusually bad for me in that I'm visiting with family but I will get back with you.
On another note you can download up to 100 listings at a time. The offset value represents a number of where to start. That is if this number is 200, the first listing downloaded will be 201. From this you can determine which listing is causing the program to hang. On my improvement list is the ability to see which listing numbers are being downloaded as it happens. This would help in troubleshooting this problem.