What router/AP is it?
If it works, then it's happy days.
If it isn't reliable, get an Ethernet adapter for it, you can even get a power-line adapter (these go through your electricity sockets) as well so you can essentially hard wire it from anywhere in your house without having to lay huge lengths of cable.
There's a huge zone of acceptability. As long as you're getting, say 10mbps, you're fine.
Pull up fast.com in the fire stick browser (Firefox and Silk are both in the Amazon app store) and verify you're getting at least that.
You won't notice a difference between 10 and 100, since streams are usually around 4.
I'd hard wire mine to the router to get your best speed. That's what I do. Luckily here in Europe I've got 300 mb/sec.
Go with Cat 6-7 cable. Wifi will come to issues when electronic devices interference happen without you knowing it.
I use my Firestick on my Wireless 5ghz network and have no problems at all. You need to ensure you have a good router. If the router is not close the firestick use the 2.4ghz network as that has better range.
I see a lot of people saying to hard wire your fire tv but they must have shitty routers. There is honestly no need if you have good hardware.
As close as possible or in direct line of sight from the router would be ideal.
Best distance?
How about however far your garbage can is from your router? haha.
If you want to watch IPTV, you really need to invest in a device that can be hardwired to your router. Wifi is the enemy of IPTV stability.
Depends on router, speed, location, and other obstacles in the way (other networks, walls, floors, etc.).