I know you say you can't function without it, but I reassure you definitely can! It's just NOT easy to get to that point.
I was told no caffeine whatsoever earlier this year in February. I was diagnosed with a disease that was sending my pulse into a tizzy. I haven't touched caffeine, still, to this day. It was very rough and I'm a single mom and had an active 6 month old on my hands. Before February I was drinking at least 2-3 cokes a day for the last 8-10 years, I had horrible withdrawal symptoms when I had to cut cold turkey. Migraines, constant crashing, no energy, bitchiness, etc. The house was a mess and some chores were dragged out quite a bit.
But, I feel so much better without it and sleep better too. I went into freak mode when they told me no more and thought to myself how the hell I would ever be able to survive without it. The first 6 weeks were pure hell but little by little you'll feel great. I've actually learned that my caffeine consumption was making my energy levels worse.
And it sounds like only the reason you need 2 cups is because of your insomnia caused by the second cup lol. If you're not getting good ample sleep your energy levels are going to be zapped for the next day. If you don't want to quit then I would seriously cut back to 1 in the morning and try other ways to boost your energy. Take a walk outside, exercise (sounds counter-intuitive but it's not), have a healthy snack in the afternoon, drink more water, etc. There's all sorts of tips for energy boosting.