Glad to hear the tileset is working out for you! There aren't any specific tiles for a closed door on a side wall but you could try putting a carpet beside the wall to indicate to the player that there is a door. Something like this:
That depends on what you're looking for. You can reach me over email (trislingames@gmail.com) with more details on your project if you want to discuss further.
As for this asset pack, the only way to purchase it right now is here through itch.
Whoops, thanks for the reminder, I knew I was forgetting something. Added license info to the description above. You can use these for any commercial or non-commercial projects.