It highly depends on the specific school and your path. If you’re in the US, and plan to go to med school it’s discouraged to use highschool credit to test out of med school pre-reqs as it doesn’t demonstrate understanding truly at the college level. Sometimes IB and AP scores only test out of beginner subject levels and it might not meet the course requirements. You’ll have to check websites for the specific schools. As a neuro major I’d recommend retaking bio

Definitely apply to NIH (or other institute) postbacc programs unless the tech position is with a well-known professor who you can trust to support you for future PhD applications. The reason being is that postbacc's are explicitly there to support future graduate students and so there are mechanisms in place to make sure you are getting good training. It also means the participating PI's are supportive of getting their trainees to grad school vs. maybe a professor who wants to keep a tech for as long as possible.

Also, the topic isn't so important. The quality of mentorship is what you should index against. Your interests will change and is probably just a function of previous exposure so I wouldn't necessarily make that a deal-breaker for you. However, if you are interested in semi-computational work for decision-making at the NIH and want a good mentor, I have seen good outcomes from postbaccs through Bruno Averbeck.

And I should clarify,I know astrobiology is a large interdisciplinary field and I am working on seeing which part of it I am wanting to go for:either back to astrophysics, microbology, chemistry or earth and space science.

I think doing a masters and then doing a PhD is a tremendous risk. You would be paying a bunch of money for a masters, and then going into a low paying PhD two years behind in a bad academic job market.

IMO you should go all out this year and try your shot at prestigious PhD programs. If you don't go in, I think you should just do your masters the next year and go into industry.

For neuroscience, the go to recommendation is Kandel et al., Principles of Neural Science. This is a typical text for a 1st year neuroscience grad student.

For sleep, Chapters 1-64 of Kryger et al., Principles and Practice of Sleep Medicine (the rest is the applied sleep medicine part). This is the desk reference for sleep researchers.

As for doing research outside of going to school, you probably want to look into doing research at a academic medical center, university, or industry. There is a lot of opportunities for someone with strong computational skills in sleep research. Everything from modeling neural communication during sleep to monitoring fatigue. People are always trying to develop better hardware and software for measuring sleep and making predictions.

As for dreams, you have to be a little careful because you can get into some pseudoscience pretty quickly. This is an interesting recent article that demonstrates what is to me interesting research in dreams.

https://www.cell.com/current-biology/fulltext/S0960-9822(21)00059-2#%20

You might want to also look up work by Matt Walker and Bob Stickgold.