Turning 30 was a lot harder than turning 40 or 50. While what I experienced wasn't how I understand a typical midlife crisis manifests, but I usually refer to it as my early onset midlife crisis.
Both turning 40 and turning 50 was much easier. In fact, turning 50 hardly registered beyond "whoa, was that my 40s done with already? Okay".
I got out of my 30 year crisis by starting to challenge myself in other fields. I've always been eager to learn, but around 30 I realized that I should make an effort to understand things that are outside my chosen field and try to do them well. And I sometimes did. The failures I didn't obsess over. Let it go, move on. And it became somewhat addictive. I try new things every year. Some things stick, others are just interesting experiences.
I also noticed the importance of changing fields regularly. On average I tend to stay in a field for 5-6 years before going off to do something I usually don't know much about when I start. In fact, approaching a new field is in itself a skill that has great value.
I've had roles from developer in a startup to VP in a large company. Having experience from many fields, and from very different roles builds a kind of general, broad expertise that is very useful. It can also make you comfortable with situations that most people would find extremely challenging.
You have to build some form of psychological resilience. Learn to accept the things you can't do anything about, and focus on what you CAN do and what you have to do. Complain if you must, but make sure that it isn't your inner focus. Don't let feelings of hopelessness take root. You have the capacity for doing a lot more than you think, but hopelessness and self-pity can block your view of that.
Along the way I had kidney failure, 2 years of dialysis and eventually a kidney transplant in my early to mid 40s. This is where the psychological resilience I had developed since my 30s paid off. Sure, I was physically in such bad shape and one point I couldn't walk half a mile to the store without having to sit down and rest for 15 minutes twice along the way. I slept 14 hours per day and I nearly died a couple of times.
Years later, most of my memories from that period are about the things I did. Not my medical hardships. And I did accomplish a lot in those years.
(Observation: a lot of people who were just acquaintances stopped by and spent time with me when it looked like there was a good chance I was going to die. This taught me something important: you may not fully understand to whom you are important and how many people appreciate you. You have the chance to show them appreciation. No kidney failure needed :-)).
As for the social aspects, having been with my wife for 27 years now I know nothing about dating. Not that I ever did. Sorry. Can't help you there.
I'm dubious about the advice to get kids. It feels a bit immoral and self-serving to tell someone to create a life just to solve some problem you are having. I think one should treat human life with a bit more respect than that. It's not a pet and you should have kids for the right reasons.
If you try out new things (work, hobbies, interests) those are generally how you meet new people when you are an adult.