Welcome to ECF and congrats on giving up the analogs. Like you I went straight into DIY and I can, at least, share my experience. First of all, I have over 150 different base flavors, so I can pretty much make anything. I vape one flavor daily, as does my wife. The good thing is now I can make 150 ml batches. The flavors will go bad long before I will use them. Second, I've tried maybe a couple of hundred recipes and didn't like most of them, so the recommendation to only mix 3ml batches is right on. Second, the 100mg nic is dangerous, but if handled with care, i.e., wash anything off the moment an accident occurs, then it's not terribly troubling. Do use safely gear, a splash in the eyes, for example, can cause serious problems. Nicotine will penetrate the skin barrier, but 100mg nic is a 10% solution, so the absorption is slow enough to be safely handled very carefully outside of a lab. Pure nicotine will kill every living organism on Earth and is used in fumigation to do just that.
Sounds like you may know what you want to make. That's a giant head start. My goal was to somehow become a master mixologist or something. I found out rather quickly that I don't have the time, the skill, the patience, or the knowledge to accomplish that goal. I have a few recipes that I like, fewer that I actually make. Lastly, I have spent way more on DIY than I would have buying various eliquid sampler packs to figure out what I like. My breakeven is probably 2020 or something. Yes, it is way less expensive to make your own juice. However, the learning curve is more expensive than I thought initially. That being said, I had not found this forum yet at that time either, so perhaps my many mistakes could have been avoided. My bottom line is that I'm just not good at it. I have dozens of flavor chemicals that are used to create the flavors. I've learned that mixing two fruit chemicals can produce a tobacco flavor. These chemical names are just that, they don't sound like anything you would ever buy as flavorings. It's really an art to create many flavors. I'm not artistic I guess. If I could go back, I would probably buy samples of top juices from about 20 different vendors to find out what I like, what's out there, and then maybe zero in my favorites to DIY. I have no problem using a flavor calculator. Pretty easy once you try. Most recipes have the percentages that you need to make a particular flavor, so it's fairly easy. What's hard for me, is making something I want to vape. I don't think that I have saved money going this route, but with the right guidance, in hindsight, I see that it is possible. Anyway, that's my story. I wish you good luck and the truth is that the JOURNEY is what makes it fun and fresh anyway. No matter what, you cannot go wrong, whether it turns out to be a panacea, or not. Enjoy the journey and happy vaping.