Pics of the rda and batteries would be helpful. Kanthal and nichrome are similar, but nichrome is lower resistance per inch so if you do the exact same build kanthal will have higher ohms. I like nichrome because it heats up faster. If you want to try kanthal id start here https://www.amazon.com/dp/B00JTGYS40/ref=cm_sw_r_awd_ZcNJub0C3B1QQ
Don't buy batteries on amazon too many fakes, save up and get some legit vtc4s or Samsung 25rs from lightning vapes. Very cheap and authentic. Also wouldn't recommend buying attys on amazon.
Check /r/ecigclassifieds you could probably find an atty cheap and maybe even trade the amazon cards for it.
I got sick of dealing with keeping my copper mod clean so I wrapped it with this stuff
Https://www.amazon.com/dp/B007OXCIB0/ref=cm_sw_r_awd_AeJHub1J9PN7V
Came out pretty nice
https://www.dropbox.com/s/p5ckg0dm8cl3ke1/2014-12-17%2016.04.56.jpg?dl=0
Though sanding and a clear coat is a good way to go if you like the copper look.
That sounds like a ton of hassle to verify authenticity. And knowing the capacity matches what it should doesn't necessarily mean it's legit. Would be more reasonable to buy from a trusted seller and learn what to look for to spot fakes. This should help
http://www.sun-vapers.com/how-to-spot-a-fake-sony-vtc5-battery/
No idea on your last question, you'll have to do some research to find what kinda amp limit it has.