No dogs are shown dying in the story. A character is said to had adopted a pet dog in the past, and it passed away. It is referenced multiple times, albeit infrequently. Most references to the dog are condensed to sub-episodes or card stories.
Multiple characters have child abuse as apart of their backstory and physical abuse is explicitly shown in the event story "Prelude to the Festival and Miracles." (also known as East Prelude)
( spoilers ) the character is not really a child in wizard logic but just in case there is a character who takes the form of a child who is dead. the death doesn't happen on screen but it's talked about
A character is said to have been hung in the event story "Etude of the Melancholy Sunflower" and there is a noose frequently shown throughout the story.
A character uses a rifle as their weapon and owns many other guns (displayed in their room.) In the event "Paradoxroid" multiple characters own guns and point them at other characters.
A snake is shown in Mithra's 2022 Birthday 4koma. There is also a snake in the event "Ballad of an Innocent Weaver Girl." Snakes are frequently referenced in the main episode of the Town of Glory location. A character is said to have a fear of snakes that is brought up occasionally.
Alcohol is VERY frequently shown throughout the story, however, no character is explicitly stated to be abusing alcohol. There is a character who is told frequently that he drinks too much by another character, however, in most scenarios this is played off as a joke.
Needles/syringes are NOT used, however there is a doctor character that occassionally references them. In the "Cat Robe" Figaro 4koma, a giant needle is shown, and multiple characters in the Rhapsody of the Clinic Where Flowers take Root (South Rhapsody) are wearing needles on their outfits.
Dragons are said to be extinct animals in the world the story takes place in. However, some dragons have been revived and are seen throughout the story. No dragons are shown dying.