You cannot run the disk version from an SD card directly, since it has a dedicated disk loader. What you can do is to load the game directly as you already did. But instead of typing RUN you have to type SYS 2064 and then press enter. Then the PAL version is started. Or you try the cracked version from csdb.dk.
Viewing post in Deathflood: Dungeon of Doom (C64) comments
I use FB to find the .d64 file, do in it, select game, and click enter. Bottom of screen fills with stuff and then the black C64 screen. I then type sys 2064, get a bunch of stuff at the top and then a dead black screen. PAL/NTSC (my monitor can do PAL or NTSC, but the C64 is jumpered for NTSC (I think there may be a resistor change also to change it to PAL. Never the less, even as an NTSC C64, it should be doing something. I just got the SD2IEC, so I am still not sure how to use it yet. The only think I know so far is to LOAD"FB",8 then type RUN to use their file browser. I have Death Flood under a folder of its own and then the .d64 file under it. My apologies; it would be best to have a floppy, but I have no idea how to make a single sided 5.25" floppy. I do have the 1541 drives, but know way to download a file off the internet on my modern computer and make a 360K 5.25" floppy. I may be able to do a 3.5" floppy, using util software and a USB 3.5" floppy drive, but I do not have a commodore 3.5" drive. This is why I ordered a SD2IEC device. Maybe it is not a good solution either. So I am not sure what to do at this point.
I wrote a small article today, where i describe how to get the game started on real hardware via disk or Sd2iec. You can find it here: https://www.windigo-design.de/wp_articles.html