VPS will give freedom of software you can use on the server, the resources are reserved for your VPS account, example: you can have nginx instead of Apache, php 5.6 instead of default 5.4.
Try PayPal, Stripe or Braintree.
I will not recommend to use 2CO as fees are very high and their fraud system is very strange, as they do accept the order and when you dispatch or process a couple weeks later they can reverse transaction without any dispute or chargeback from customer.
Stripe allow to exactly the same PayPal Pro, example accept payments via phone or fax, as they do have terminal in their control panel + you will be able ro connect to your website via API or html form (very easy to integrate)
the best SEO tool for beginners
https://www.google.com/webmasters/tools/
as it will also describe what exactly need to be done to improve the google index.
Bitcoin is most protected from fraud, but it's very complicated for any non tech person to use it.
I think the best payment providers are: PayPal, Stripe, Paymill, Braintree, Nochex
PDF file can be open on any device, including Kindle (simply send to kindle email and it will be converted to kindle), as for kindle file format is designed for Kindle only!
No, as based on a few of my personal domains, the 12 years old domain name has exactly the same PR as it was 7 years ago, anyone nowadays can have the whole website indexed by Google and normally result will appear within 3 - 7 days.
I don't think this will speed up the Wordpress, as much better to use server side optimisation than overloading the Wordpress with various modules.
nginx + Fast-CGI + cache
https://danielmiessler.com/blog/ultimate-speed-wordpress-nginx/