Remove the period at the end of my link, most clients should automatically, but in hindsight not the best place to punctuate anyways.

Personally, no I have not tested it, however it should be the same as a regular debit card, which I know through testing that they accept, and a quick internet forum search says they do accept Visa gift cards.

If you generate a brand new wallet, convert your monero to bitcoin, and then pay Proton, there's very little to trace back to you.