I'd like a second opinion: Did my dentist mess up my masseter Botox by injecting too high? (Photos)

I will start with a short answer. Looking at your pictures and assuming you were trying to smile the same, it is most likely that your risorius muscles were injected. Maybe part of the zygomaticus major muscle was affected as well.
Typically to achieve a full effect of face slimming (muscle atrophy), 10-12 weeks is required.
Unfortunately, your side effects will also taper over 2-3 months.
It is true that there are various bellies of the masseter muscles, such as deep vs superficial. An injector should be assessing the optimal location injection to achieve the result that you desire. Unfortunately, many injectors are simply taught the "paint by number" method over a short seminar.
The hairline injection sounds like your injector is also trying to treat the temporalis muscle. Again, a single point is not very ideal since the muscle is a wide and strong muscle.
I would highly recommend you receive future treatments from someone that is actually knowledgeable on this topic.

Botox is a muscle relaxer, and in the masseter muscles is often used to create a jaw slimming appearance, so that is most likely the effect you are seeing. Botox is temporary and only lasts 3-4 months, so it is not permanent. However, I highly recommend getting Botox injection treatments from a provider that is specifically experienced/specializes in cosmetic injections.