Yes. I reset my career 3 times between 30 and 40 and I did progressively better each time.
-Is there any reasonable path to starting over?
No. Jump into it. Be unreasonable. Fail fast. Accept lower seniority positions if it gets you in the area you want to work in.
-Where do I even begin?
LinkedIn Jobs, trade shows, old friends and former coworkers. Hit up on LinkedIn founders and upper management of the companies you want to work with, you would be surprised how many have answered me back over the years.
-Will tech co’s ever consider hiring someone like me?
We live in credentials bubble where everyone has a piece of paper saying they are a senior specialist on yadda-yadda, but finding someone who is lean and mean, hungry and means it, who would be willing to work 12 hours a day to bridge the gap and overtake the rest of the team? That's really hard.