40 year old tech entrepreneur is an amazing job title and past experience!! Startups will be lucky to have you! Apply at positions, meet founders in your network and share with them that you are wanting to now help startups grow having done the same at yours.

Passion ends when the grind starts and you are involved more in day to day activities. I would suggest below:

Do you want to give startup shot once again and rekindle that passion back. Take a mindfulness break and visit a wellness retreat which will help with peace and clarity. And if you get an answer yes you want to continue, distribute your time- 1-2 days to new feature launches which will keep passion alive, two days for meeting new customer , one day for your personal learning. Take the weekends off just like in any other job. And if yes the money is an issue then move onto exploring jobs alongside your startup.

I am working in Corporate over a decade and having switched jobs myself succesfully, I would suggest couple of approaches:
1. Check on linkedin and spot mutual connections and ask them for referrals ( Invest in Linkedin premium ).
2. Reach out to Business heads / HR recruiters / leaders
3. Polish your resume well and make it look presentable. Use automated resume makers which will help.