My suggestion would be no, don't go with version 13, because it definitely performs slower than version 14. I'm not aware of any stability concerns, but the guys at FMPHost are jam up, so I would assume they've seen some issues.
Have you gone through the WebDirect guide yet to make sure your database is tuned for WebDirect?
I haven't done that, but I'm not sure how important it is. There will be just a handful of people using this database, and if it's the general consensus is that using the FM client is more robust, and more stable, it's probably worth it to just do that. I was really just curious.
I'm not for familiar with the expression "jam up". What does that mean?
Means they're very good at what they do. Southern thing. Or "thang", if you prefer.
The design of your database is very important. When you have a lot on the layout, for example, there's a lot to refresh. So the connection is kept very busy. Simple layouts, using themes, work better. The fewer objects you have on the layout, the better off you'll be.