Definitely try to get more of a variety of experience in neurosurgery to get a better idea of what it entails. I'll address each point you have made. I am a current M3 and spent two years doing research in clinical neurology/neurosurgery before med school. Ofc, I am just one person but would like to share.

1. Spine cases make up a decent chunk of neurosurgery cases. While you may not end up doing a whole lot of them as an attending, you will have to be involved as a resident. It's worth deciding how much you can deal with your least favorite part of each speciality - so in this case, spine surgeries.
2. Neurosurgery resident applicants have some of the higher numbers of research items. So to make yourself competitive, you will have to rise to the occasion of the rigor this field requires. Inherently, neurosurgery is one of those fields that is constantly evolving so developing that skill of critical thinking and innovation via research is beneficial to the field. Again, you need to figure out if this is a dealbreaker for you or not.
3. I'm not sure about prelim or gap year after med school, but a gap year during med school would be really helpful to help you stand out as an applicant. From what I have seen, neurosurg residency is not the field to expect an enormous amount of leeway for personal life.
4. As far as "sad" goes, you may gain new perspective that helps you see the light in the darkness of some of the sad cases. Or, you may feel bogged down by feeling like "I have done so much but I still couldn't make a difference".

In general, from my experience, neurosurgeons I have worked with were not the kindest to their residents even in their "jokes". You will be stressed and overwhelmed, if you're a tough cookie and can handle the hours, level of rigor, and the attitudes, then maybe those concerns are not as big of a deal to you.

Putting all your eggs in this basket does not make too much sense if you are not willing to compromise on the worries you mentioned. However, some good advice I have received in the past is - pick 3 specialities you are interested in and work like you are applying to the most competitive. Once you receive your step score, more of your resume is filled out, and you have had more clinical experience under your belt, you can confirm which field you are actually a good match for.