Re: step one: ring your card provider
I used one of those cards that allows you to relegate a unique card number to each merchant you buy from
Yeah. I've been using virtual cards from privacy.com for any card-not-present transactions for a while now, and I have to say I've been pleased. Create any number of cards, set various limits (per-transaction, daily/weekly/monthly), restrict to a single merchant, various options for being notified of any transactions, and you can use any name and mailing address you like. It's all tied to a bank account, so if you want an additional layer of security, you can open an account specifically for those cards.
They make their money off the merchant fees, so it's no additional cost to the consumer.
The web UI is fancier than I prefer, but it's not too obnoxious. Works fine with non-Chromium browsers.
I don't have any relationship with them beyond being a user of their service.