Here are some Halloween-sounding songs that I could see you guys playing. They are metal songs, but not super fast. They also aren't black/doom metal, but they're doomy enough imo to suggest:

Uneven Structure - Succube & Funambule (These 2 songs are next to each other on their album's track listing, so Succube will end abruptly on the video I linked because it transitions into Funambule.)

Leprous - Passing (I think this one will work best for you guys.)

Between the Buried and Me - The Future is Behind Us (For this song, I suggested it because the second half of it is heavy af and when watching the music video, the song seems more eerie.)

Gojira - Vacuity (I can definitely see you guys playing this.)

Also, the first 3 songs listed contain a mix of clean & harsh vocals and the 4th song is purely harsh vocals.