Consider your Firewall too. I know when I last experienced constant 9002 errors it was because of ESET Smart Security blocking all the server requests for the authentication and game servers. Either port forward on a static IP or put the game into your firewalls whitelist. Ofc this does not guarantee a solve, I've also noticed it block a few other IPs (I'm guessing they're backup servers on SEs end) that are blocking the games access. Luckily I'm using the beta of SS9 so I can whitelist common blocked events from the game straight from the main ui and with permanent rules. Since I've done all the above, not a single disconnect.... Sure, SE servers might have probs, your ISP may be being a dick. But before all that. Check your own hardware/software.
While I cannot address your other concerns, in regards to the 90002 errors, I was experiencing the same problem a couple of weeks ago. Early in the week, it was maybe once or twice a night, but the following weekend it was every 5-10 minutes, which annoyed me enough to investigate it. In my case, the issue was due to a bad node in my network path to the FFXIV datacentre. The path I was taking was via a node in France which was experiencing significant packet loss. I used a VPN to alt-route my traffic via a different path and I've yet to experience a 90002 error, since the change.
Hmmm ive been running this bot for a few months now, not once has a 90k error happened while running the bot, but it has disconnected me while playing on my own without bot use. RB hardly ever shuts itself down due to an update. I run it for days and then turn it off and resatrt to find a random update that i didnt know was there. RB has been working above and beyond what i expected from it. You cant expect it to be 100% functional when a major update has just happened to the game. In all practicality be happy you have access and have the luxury of using the bot. When its down, go experience and enjoy the game yourself. Id check into your ISP/network connections. Thats where your problem is, not RB.
I posted this before, but I think I'll post it again. https://en.wikipedia.org/wiki/Correlation_does_not_imply_causation https://en.wikipedia.org/wiki/Post_hoc_ergo_propter_hoc Basically just because two things happen together doesnt mean they are related. I run up to 12 bots at a time and have no issues with 90k. If your having issues then first I'd check your hardware and make sure you aren't running low grade equipment. Personally I use this (https://www.ubnt.com/edgemax/edgerouter-lite/) but if I was buying new I'd probably get this (https://www.ubnt.com/edgemax/edgerouter-x/). Second I would check to make sure my internet isnt dropping out, easy check is open a command prompt "ping -t google.com" if you see any drops then there you go its your internet acting up, complain to your isp. Third, all future updates will only remove features and degrade stability. I think I will remove combat assist and then fatebot, and perhaps orderbot. I think making actionmanager.cancast return random values is also a good idea.