How strong would you make this master password and where to save this one?
Are you familiar with https://xkcd.com/936/ ?
And I really think that finally someone *has* to come up with some replacement for this password nightmare. Some kind of hardware key maybe.
Yes, they exist. https://www.imperialviolet.org/2018/03/27/webauthn.html is a comprehensive introduction that will give you terms to feed Google, and his https://www.imperialviolet.org/2017/08/13/securitykeys.html compares some of the keys then on the market. Yubico do well, IIRC.