I'm back for more!
So I started fiddling with Sacred once more. And after some testing, I was able to beat the game's stubborn windowed mode and got a nice standard Window going, which can be resized, moved and functions like any other standard Window. Also, I finally can alt-tab out of the game and it doesn't stop working!
So to do this, I actually had to leave the game set into Fullscreen mode (Via config.exe), then I used dgVoodoo2 to force the game into a window, and it actually works.
DgVoodoo has an option to set the resolution to biggest possible window while keeping the aspect ratio 4:3. Due to my screen resolution I made some quick screenshots at 1280x960, but feel free to test it out at your desktop resolutions. Also, the new version comes with an option to force different types of texture filtering, but I have yet to see any difference: https://imgur.com/a/V0aIT
PS: guess the anti-bot defense is still against me