It looks like the server was going through a scheduled restart when you tried to connect. It restarts every day at that time, but it's usually back up and running within about 5 minutes.
I believe they are infinite. They're just spaced out from each other. If you want to get a better idea of how they tend to spawn in relation to each other, you can check out Nether Fortress Finder - Minecraft App and try different random seeds. This might give you an idea of how far you should expect to travel in a given direction before encountering another fortress. You can find some additional tips here: Nether fortress – Official Minecraft Wiki Hope this helps!
hmmm i couldn't find any chests in the nether fortresses, but that was before the reset. i still need to find some!