Maybe your keys leaked with the 26 ETH transaction that you made from Metamask to your Kraken account. After that, someone got the secrets that they needed to steal the remaining coins. I don't know how, though.

My intuition leads me to this conclusion as it appears to be the most logical, but from a technical standpoint, it feels like a stretch.

What about your partner that you said lives with you. Does she use your computer? It doesn't have to be that she stole from you, maybe she used some fake app. Does she play games or use some dubious apps and permissions over social media?