Unfortunately I stored my seed in .txt file
I'm gonna create a new wallet with Electrum, give it a much better password, store the seed on one of ye old pen & paper devices, like a notebook.
While storing the seed on actual paper is much better than a text file, I recommend to keep 2 copies of that in different places.
But the main reason for my answer is that since you don't know how the hacker got to access your txt file, especially if that file was only on your computer, I recommend you do a proper scan/disinfection first.
And yeah, please verify properly the downloaded Electrum.