You need Internet service from someone like Comcast or Verizion to start with. From there, you could use thier modem/router. From there, it depends on the devices in your house, if they have wireless, you should be able to connect to the router and get on the internet. If not, you would have to be hardwired with an ethernet cable to the router.

No, that model does not appear to have an integrated modem with it.

Conceptually yes. I really depends what features you have turned on with your Verizon router vs the ASUS router. For instance, only one can be the DHCP. You could use the Fios router as you main outbound connection to the internet and then use the ASUS in bridge mode and have all of your wireless connection come through the ASUS. Probably several options you could do.

That is not an easy question to answer. The best i can tell you is that the 5g is able to penetrate walls and ceilings, but the 2.4g penetrates much better. It might be good to do a dual band router so you have the option of switching in case your 5g band gets slow.

You could use a second router with exact same wifi settings, some people do that instead of an extender. There is also ASUS 1900 package that comes with an extender, and I think they sell it separately for $60.

Usually people are stuck with the location, they tend to have it next to the cable modem. The nighthawk seems to have good range in my large 3 story house.