Is it crazy to become a luthier?
There are full time schools to learn the art of luthiery.
It's not crazy. The first step would be go investigate what courses etc. are available that you could attend. Nowadays I think there are specific instrument making courses. I doubt you'll ever be rich but it must be a fascinating, fulfilling occupation - the opposite of dull and boring. Good luck.
Not if you enjoy it and want to do that. It's not likely to make you rich but you can make a living if you do it well
If you are in a small town, you might not make much. If your are in or near a large city, you might do well if you are good.
No. Keep practicing as a hobby and improve your skills. Buy old / damaged guitars etc. and renovate them for sale - that's both practice and profit. Take plenty of photos and it also gives you advertising info; and the sales will start to build your reputation with other people and spread word that you can do the work. See how it goes - if you get enough work in, you can decide if you want to do it full time! I buy the cheapest, nastiest condition guitars from a couple of local secondhand shops and occasional old worn or damaged ones on ebay and renovate / refret them as a hobby; I don't don't make anything much on them but in my case I don't want to do it full time, I just enjoy the work.
I see nothing wrong with it. Someone’s gotta fix broken musical instruments. Never know, you may start your own business someday.