Yes. your first problem is you're using datacenter proxies. That is almost always going to trigger blocks because no real user is operating on a datacenter. Residential socks5 are going to be your better choice. Check out PremSocks, ipburger, or faceless.cc
Yes
Yes. I've bought 2 different accounts from him (a bank account and credit card). Both were delivered quickly, with great instructions. One of my favorite vendors here.
You weren't scammed by Nemesis. Nemesis is a marketplace. So either you were scammed by a fake fishing site, or were scammed by a trash vendor on there.
There are many legit vendors on Nemesis. If you're unsure about trustworthiness of one, try going to dread and seeing if there are any reviews...