Those threads are mostly full of recommendations that don't make sense. There'll be a couple actual recommendations of merchant account providers, which will have the exact same policies for reviewing accounts, freezing them if there's any red flags, holding funds for the exact same 6 month period, and forbidding factoring as PayPal cited in this case. The other recommendations will be for payment gateways (which do nothing without a merchant account) and some people throwing out names of the hot new subscriptions-as-a-service providers (Recurly, Chargify, etc) which again do nothing without a merchant account and have nothing to do with their policies.
The provision forbidding accepting payments on behalf of others is going to appear in the merchant agreement everywhere you look. It's standard. It's not a PayPal thing.
No browser is standards compliant. That's impossible; the "standards", at least pre-HTML5, contain ambiguities and self-conflicts. It's all a matter of degree. And I can't agree with your assessment, Microsoft has shown interest in improving their standards support repeatedly. Each browser was closer to the mark than the last.
The ad networks and such will just track you through browser/device fingerprinting instead of cookies. Except for extremely tightly controlled, homogenous systems in corporations, it doesn't take much info beyond your IP and user agent to uniquely identify a PC. Your history/cache, fonts, plugins, screen/viewport size, etc. are all discoverable from the browser.
I have the very same app 80% complete. I haven't launched it because of all the caveats with international numbers. It's hard to try to sell this to web stores and the like that take orders from around the world if I can't support half their customers' numbers.