I'd go with... for the first 3 years live on 40K a month (easily done outside of Bangkok) - then after 3 years, you'll have the 800K in the bank to safely ignore the income requirement.
Brexit would be my biggest immediate concern because while I don't see a likely 20% slide in the pound... that's a big grey area to flesh out. Otherwise, you should be able to coast for 3 years and then forget about it.
Once you have an ED-Visa in your passport, you are not asking for a visa waiver and can enter by land without issue (assuming immigration don't find another reason to deny you).
You appear to be completely bonkers - nobody was entering into such a discussion. Blocked because I can't tolerate this much stupid in my day. Goodbye.
Yes. You can stay for up to 1 year without exiting, you need to report every 90 days when you do so. You do not need a new visa for 5 years. How is this inconsistent in the slightest? Though, it's worth noting 90 day reporting is very, very easy for Elite visa holders.