Stuck and looking for a hint!
--spoilers--
I have the crown and I got the sandwich to Don. I see the etchings outside of Bat-Son's bedroom. I tried entering the 3 runes I see at the top into the crown but putting it on the snowman yielded nothing.
I also saw mention of a shovel in the comments (and in the gameplay video), which I wasn't able to find despite searching everywhere I can think of.
Any help would be appreciated!