kyro - I want to congratulate you on your decision! I went through the same thing (graduated in 2011) and it was indeed very difficult at the time. Over time your friends and family will come around and realize you made the best decision for yourself. Work hard, find a great mentor, and enjoy the ride !
tmux really shines for me when starting or switching between projects. I can fire up a rails app with a single command and have all the tabs I like ready to go. Check out prag prog's tmux book for a quick intro: http://pragprog.com/book/bhtmux/tmux
You're going to be successful no matter which road you choose. You have skills people value that you can always use. Not knowing more about the details, I say go with the new opportunity with the guy that seems to want to work with you. Who do you want to spend the next x number of years with?
But information technology is what I know, and it’s probably too late for me to learn a new field from scratch.
Information technology can absolutely save lives - I'd argue that a developer building medical software can save more lives than a PhD working on a treatment for cancer. The subtle killer these days are all the extra days a patient spends in the hospital. An extra day or two is what leads to complications. Work on solving the inefficiencies of inpatient medicine (documentation, communication, decision making, ect.) and you can go home at night knowing you are literally saving lives with your programming skills.
It would be cool to somehow use a digital scale to track supplies. Each time you weigh a reagent, the scale could enter the amount used into Quartzy.
Come to think of it, using NFC might work really well for logging supplies. Stick a NFC sticker (I bet tagstand would hook you up) on items you want to track.