So... to sum up: you want to take caffeine on your E-juice because this way is quicker, but also remains less time on your system than when ingested orally. That way you can´t take it at late night and be able to go to sleep soon after... ...what about rapé(joking)?
I don´t know man, sounds like you need help
.
Also, regarding caffeine (in my studies you have to stay awake all night and I would take a lot of diet cocacola, coffee and sometimes monster or redbull), withdrawal is real, but nothing deadly, I would just feel sleepy... sleep a lot for 3 days in a row, I guess you can´t go to work like these.
Then you never feel as good as when on coffee... but it depends a lot on your diet. Having a low carb diet to avoid insuline peaks, arrange several small meals a day vs 3 big ones than makes you sleepy, eat green smoothies with spinach, doing cardio, sun exposure... etc. If you really do this and still feel like shit, then go to see the doctor.
About the ADHD (I´m dislexic and childhood hyperactive myself), these days is like a deus-ex-machina, dark, bottom-less bag where a lot of people are thrown, you might as well diagnose yourself witchcraft, communism or gender bigotry.
bestluck
"...after five seconds I was no longer a marxist, no longer a materialist, no longer a rationalist.
It killed those things, it cauterized them..."Terrence McKenna