First off, take a BIG, DEEP, BREATH! This is not the be-all-end-all. MANY freshmen (sophomores too and some juniors) realize that they are not cut out for the major that they chose and pick a different one. That is okay! Make it through this semester and try fulfilling some general requirements (Gen Eds) next semester. This will give you a chance to explore some other areas you may want to major in. If needed, drop the chemistry class. No one will fault you over having one W on your transcript.
Most importantly however, and I cannot emphasize this enough, is that you are NOT crazy, but you certainly need to see a therapist ASAP. Your health, including your mental health, should always be your priority. Having suicidal thoughts does not make you crazy, but it does mean that you need to see a healthcare professional immediately!!! Be your own advocate and call your student health center or some other health care provider and tell them that you need to see a therapist TODAY because you are having suicidal thoughts. If you are told there are no appointments today, keep dialing healthcare providers until you find someone who CAN see you TODAY.
If you need to talk to someone immediately, please call the National Suicide Prevention Lifeline: 1-800-273-8255. Nothing, especially a college chemistry class, is worth harming yourself over. I don't know you personally, but I guarantee you that the world is a better place because you are in it. Hang on. Get the help you need. It WILL get better.
Yes, of course this would hurt your chances. Colleges take plagiarism (both the one who does it and the one who enables it) extremely seriously. If you are asked about honor code violations, then I feel that you should answer that honestly and unfortunately the honest answer is yes. I think usually they give you a chance explain. (Not 100% sure as I never had this problem.) You can then explain you were a stupid sophomore who wanted to help a friend by allowing him/her to copy your work and that you never have and never will ever allow that to happen again.
Even if it is not on your transcript, it could be mentioned by your counselor. I personally think that it is better to own up to your mistake and explain that you have learned from it.
No, you should not contact colleges about what they consider a hook. They likely won't tell you. Apply for schools that you are realistically qualified to attend (matches), schools where you are in the top 25% (safeties), and a few reaches, if desired. Then let the chips fall where they may.
Agreed with Eeyore above. Taking AP chem might be a big help to you because college chemistry is much more difficult than high school chemistry, especially if you haven't taken AP. AP chem is basically first semester gen chem (at least at my university), so they cover in a year what colleges cover in one semester. Having seen the material will gvie you a big advantage and may allow you to focus a little bit more on some of your other classes.
Good for you, though, for having taken so much physics!! I feel like I spend a lot of time on this site trying convince high school kids that physics is important to take in high school.