Delegation is necessary but it hard the first few times. It takes a lot of getting used to because very few people are going to do things up to your standards (some will do >= you which is awesome). Note that eventually these feelings went away...until I got promoted and then they came back again: 3am chest squeezes and a sense of "I don't know what the fuck I'm doing again and no matter how hard I work the needle doesn't move."
Over the years I realized this is just a side effect of new challenges with increased responsibility. You (YOU) are a natural problem solver and it takes MONTHS to come up to speed so don't beat yourself up. You will solve the problems and invent your own systems.
Finding mentors is hard, but I found some through Meetup.com of all places (bay area, austin, and portland are my haunts). Note: they're not all older than me, but they have had similar experiences. Mentors can be younger than you. And mostly they don't have specific help because at this level techniques aren't really transferrable from person to person... my startup founder friends just remind me I'm not a phony fuckup. And that matters.
Welcome to being a grown up!!! It'll never be quite as fun as being a 20-something hacking code 80 hours a week for years on end, but there are new things to enjoy with age!!! (Confession: I still write shell scripts to procrastinate because it makes me feel like I've accomplished something.)
Good luck! This sounds cliche, but remember YOU REALLY CAN DO IT, don't set the bar impossibly high. You've got the right attitude with your realization in the sentence to last. Just trust that your knack for problem solving as a coder will cause your brain to inevitably figure out creative solutions to your current problems.