I went through something almost exactly the same a few years ago, and I'm almost completely on the other side of it now - far happier and with a new set of life goals.
We are told that money and our jobs are what are most important in life. I mean, yeah, all the aphorisms deny this - "Money can;t buy happiness", "The best things in life are free", etc., but all of society is set up for us to sell the best parts of our lives to further enrich the wealthy while we're left with scraps. Your boss makes significantly more than you do, their boss makes significantly more than them, and the majority of the profits are directed to investors who contribute nothing of substance to the company. You take a job that pays well that you can tolerate - few of us "love what we do" because we're often doing things we don;t benefit from directly, are doing things we know are incorrect but that;s what the boss wants, or doing things we really don;t understand just to make ends meet. Quit your job and you will find yourself homeless and starving - at least, that's the message.
You need to recapture the meaning in your life. I worked like a dog for years, traveling the world, leaving very little time left for the family I built, the family I wanted. When my father got sick, I had to move to be closer to him, but my wife and kid had to stay behind. We were separated for seven months. That forced separation killed my soul. When I took the time to stop and evaluate the situation, I realized I was so angry because I missed them - that all I ever wanted was to be with them, that even my job was a hindrance to that. When things settled with my dad and I could move back home, I tried to figure out how to change things so I could focus more on what matters to me - my family, my home, the communities that support me that I choose to support and participate in.
I lost my job just before the pandemic, and all the interviews that seemed very far along suddenly stopped as those companies circled the wagons in the face of uncertainty. I watched my savings was rapidly dwindle. My family adjusted and started to learn to live with less - less eating out, less buying things to fill the void of loneliness we felt, etc. After a couple of abortive attempts to get a new job, I decided to just start consulting. I hung out the shingle on LinkedIn (Like you, I thought I had killed my professional network, but I have built up a lot of goodwill over the years that loads of folks were eager to pay back - I bet you'll find the same) and got a couple of clients pretty quickly. It took six months of scraping and struggling and borrowing before we had enough consistent income I could relax.
It;s been two years now. I work from home and no longer travel unless absolutely necessary. Since I don't go into an office - and since I set my workload and hours - I have more time for things around the house. My garden is improving. My house is cleaner. I cook more elaborate meals for my family because I have the time and am in the right place to go and monitor things. We home school our son (he spends some time at a co-op style school as well) and I get to help - I often jump in with math and science issues and get to teach him things like programming and electronics.
The point is not that you need to quit your job and start consulting - that may not work for you. The point is to sit down and figure out what actually matters to you. You already said it - "a wife, kids, a house, meaningful work, etc." Do you have any of these things in your life? If so, it;s time to start readjusting your life to focus on them - these are the rewards for your efforts, you should enjoy them now as life is short.
But, in re-reading, it sounds like perhaps work and life may have prevented you from finding that family. 43 is still quite young, and you have plenty of time left - truly - to find peace and love in your life. But you need to readjust your focus. Let go of the idea that your value lay in the money you make - that is an insidious lie used to control you and force you to work for pennies. We spend too much time optimizing for money as a society and practically zero time optimizing for humanity. You can't change the world - but you can change YOUR world. YOU don;t need to optimize for money. Figure out how to live comfortably with less - all we truly need in life is to be well fed, well loved, and well rested. Figure out what that means specifically for you - for it;s different for everyone - then put your focus on that. Make enough money to support your efforts in finding personal peace and happiness, but don't sacrifice your own happiness for money. You did that for 43 years - so did I - but, together, we can be done with it.
Do you wish you were a happier, more congenial, more friendly person? Then BE that person. Who do you admire and what do you admire about them? Impersonate those qualities until you can truly call them your own. And forgive yourself when you screw it up - because you will screw it up again and again. That's not a personal flaw, that's just being human. Forgive yourself, love yourself, and learn from your mistakes. It's hard work, but it's the most satisfying and will pay in far greater dividends than any job you have ever had.
And becoming a caring, empathetic person has a tendency to draw other good, empathetic people to you. Build a community of people who support you, and whom you can also support. Your friends, your chosen family, groups to which you belong that you genuinely feel improve your world - seek them out with patience for them and yourself. And make sure you stop on a regular basis to evaluate things - many call this a practice of "gratitude" or "counting your blessings". Done wrong, it's just toxic positivity - "Oh things are bad? Just count your blessings!" Done right, it can give your perspective as well as lay out the path for you to follow - "I have a lot of good friends, but I still feel a bit disconnected. Let's try engaging with them in a different way - being more honest and open, or spending more time listening than talking, or suggesting an activity for us rather than just doing whatever they want..."
If you need help from a professional like a therapist, seek it. But you mentioned having a hard time getting access to mental health services. A therapist at this point is helpful as someone neutral to whom you can speak and get everything in your head out - like laying the pieces on the table to examine them and figure out why they aren't fitting. If you can't find a therapist, find a friend. or use ChatGPT. Or start a podcast or diary just for yourself and no one else, a safe space to share and explore your thoughts. The simple act of approaching these problems with the intent to examine and find a solution to them is often enough to unstick whatever is holding you back and get you started on a path toward a better life, so try something now and don't give up.
You got this.