When I need more information on an IP address or range, I use the WHOIS tool from ARIN at Whois-RWS. This usually gives me the network range, CIDR, and probably more information than you need (Owner, Origin AS, etc).
I don't keep a backup WiFi router, but it doesn't seem like a bad idea. I guess it really depends on your situation. If my primary router were to go down, it wouldn't be a big deal as I would be able to hook up a cable almost anywhere in my home. I could also pick up a new router relatively...
It's really a matter of preference. Personally, I would stay with the Cisco SG300 as their products are usually rock solid. I've never had any issues with their support and they keep up with the IOS/firmware fixes/upgrades. If you run an all Cisco environment, these switches are feature rich...
I have a Netgear R8000 wireless router and it gives me the option under Security - > Block Services -> per schedule option. It blocks services by ports so you may allow access during the black hours by whatever ports you use for your intranet. Lets say you want to give access to an intranet...
If you need something to extend your wireless signal, I recommend the Netgear EX7000. I have a two story house with my wireless router upstairs, and I sometimes have some signal strength issues downstairs. I installed it via a cat6 connection and I've been impressed with the results so far.
I had an issue with my kids staying up too late because they were on the Internet. Taking away their devices every night wasn't a feasible solution. I ended up setting up a schedule on my wireless router for their specific devices. Now they only have Internet access from 8AM to 9PM on...
I've been happy with the Netgear R8000, but it may be overkill for your needs. The Netgear Nighthawk R7000 is also a good wireless router and has recently gone down in price.