If the app requires an internet connection I’d recommend to stop using it and just use the built in print dialog. The printer shouldn’t need constant internet connection, just a Lan connection where it can broadcast on. The printer may have to connect sometimes, for which I’d recommend Ubiquity’s mobile router, easy to manage, runs on usbc, but it is a bit pricy.

A teardrop attack likely won’t “breach” the firewall, it’s just a denial of derive meant to kick your network offline. Turn your modem off for an hour, check it works once it’s back on and otherwise call your ISP to get a new IP.

IRC, it’s ancient which may sound bad but it means that most implementations have grown mature and won’t cause issues.

If it’s constantly reading the same data it’s stored in cache, which is significantly faster than reading from the actual drive. Because the latency is average and cache is very fast it lowers the latency shown in that graph.