"The Legend". Problems with the walkthrough.

by the way, in version 1.6.3, is it necessary to marry Mirabelle in order to complete the Kraken quest?

Marriage isn't necessary, but proposing is a must. Only a great warrior is worthy of such a maiden, and the suitor must prove his valor. If you propose, Mirabelle will present her usual challenge – to defeat the Kraken. I think that's how it works.